Jane Austen's admirer Virginia Woolf said that "of all great writers she is the most difficult to catch in the act of greatness". It is a brilliant insight. The apparent modesty of Austen's dramas is only apparent; the minuteness of design is a bravura achievement. But it cannot be shown by some grand scene or speech. Accuracy is her genius. Noticing minutiae will lead you to the wonderful interconnectedness of her novels, where a small detail of wording or motivation in one place will flare with the recollection of something that happened much earlier. This is one of the reasons they bear such rereading. Every quirk you notice leads you to a design. If you ask very specific questions about what goes on in her novels, you reveal their cleverness. The closer you look, the more you see. Try these 10 questions.

Who marries a man younger than herself?

Age matters very much to characters in Austen's novels: think of Elizabeth Elliot in Persuasion, unmarried at 29 and approaching "the years of danger". The age of a young woman (but also a man) determines her (or his) marriage prospects. In Pride and Prejudice, Charlotte Lucas is 27 when she snares Mr Collins, her age spurring her to waste no time when he heaves into view.

"A woman of seven and twenty ... can never hope to feel or inspire affection again," declares Marianne Dashwood in Sense and Sensibility. She is, however, an absurd 17-year-old: judgments of what is inevitable at any given age are invariably ridiculous failures of imagination. Lady Russell in Persuasion thinks that Charles Musgrove would not have been good enough for Anne Elliot when she was 19, but once she is 22 and still unmarried, he becomes quite a catch, so quickly does a young woman's bloom fade. Yet Lady Russell is usually wrong about things, and at the ripe age of 27 (that number again) Anne gets the man she loves.

Charlotte Lucas feels all that age pressure. In hooking her husband she becomes the only woman in all Austen's fiction to marry a man younger than herself. For Mr Collins is introduced to us as a "tall, heavy-looking young man of five-and-twenty". Many admirers of Pride and Prejudice think of Mr Collins as middle-aged. In the 1940 Hollywood film the role was taken by British character actor Melville Cooper, then aged 44. The trend was set. In Andrew Davies's 1995 BBC adaptation Mr Collins was played by David Bamber, then in his mid-40s. In the 2005 film, the role was taken by a slightly more youthful Tom Hollander, then aged 38. Adaptors miss the point by getting his age wrong. His solemnity and sententiousness are much better, much funnier, coming from someone so "young". Middle-aged is what he would like to sound, rather than what he is. His youth emphasises Charlotte's achievement, with little money and no beauty to assist her.

Who says: 'I hate money'?

It has to be a bad person, for anyone who professes not to care about cash must be lying. It is Isabella Thorpe in Northanger Abbey, a youthful but accomplished hypocrite, who announces her antipathy to lucre. A few chapters later she tells Catherine Moreland, in preparation for dumping James Moreland in favour of Frederick Tilney, "after all that romancers may say, there is no doing without money". In Sense and Sensibility, another mercenary young woman, Lucy Steele, talking of Edward Ferrars, tells Elinor Dashwood: "I have always been used to a very small income, and could struggle with any poverty for him." It is the purest cant. Lucy is ruthless about money, a fact nicely illustrated by her stealing all her sister's petty cash from her before eloping with Robert Ferrars. We should not forget that idealistic Marianne Dashwood shares this supposed scorn of wealth with these two calculating girls. When Elinor and Marianne debate the importance of money in the company of Edward, Marianne reacts indignantly to Elinor's declaration that happiness has much to do with "wealth": "'Elinor, for shame!' said Marianne, 'money can only give happiness where there is nothing else to give it. Beyond a competence, it can afford no real satisfaction, as far as mere self is concerned.'"

When Marianne is burbling about the "remarkably pretty" upstairs sitting room at Allenham (just right, she is thinking, for a lucky wife), she regrets its "forlorn" furniture. All it needs is to be "newly fitted up – a couple of hundred pounds, Willoughby says, would make it one of the pleasantest summer-rooms in England". The casual extravagance of this – all the worse as it is the imagining of wealth that will come only when Willoughby's aunt dies – should stop us short. The two lovers have been thinking of spending twice Miss and Mrs Bates's joint annual income in Emma on soft furnishings for one room. Austen's attentive first readers would surely have come close to despising Marianne when they heard her saying this. It is further proof that those who declare themselves above caring about money are those who are most governed by it.

What is Mrs Bennet's Christian name?

We never know. Nor do we know the forenames of other Austen ladies: Mrs Dashwood, Mrs Allen, Mrs Norris, Mrs Grant, Mrs Dixon, Mrs Smith. A few husbands call their wives by their first names. In Sense and Sensibility, John Dashwood calls his ghastly wife "My dear Fanny", though she addresses him as "My dear Mr Dashwood". In Emma, Mr Elton flaunts his use of his wife's Christian name. "Shall we walk, Augusta?" he says to her in front of the group at Box Hill. It is almost ostentatious. "Happy creature! He called her 'Augusta.' How delightful!" says stupid Harriet Smith, after first meeting the vicar's monstrous new wife. Her exclamation indicates that the Eltons are behaving in an unusual, perhaps modish, manner. Mr Elton's flourishing of "Augusta" is made the more repellent by Mrs Elton's mock-coy revelation that he wrote an acrostic on her name while courting her in Bath.

Yet it is not simply "wrong" to use your wife's Christian name. In Persuasion Admiral Croft addresses his wife as "Sophy". This is at one with his breezy good-heartedness, and a sign of the couple's closeness. Such is his uxoriousness that, as he struggles to remember Louisa Musgrove's frothy name, he frankly wishes that all women were called Sophy. Meanwhile his wife addresses him as "my dear admiral". He is one of those men (Mr Palmer, Mr Bennet, Mr Weston, Dr Grant) whose first name remains undeclared.

The mere use of a person's Christian name is electric. In Sense and Sensibility Elinor overhears Willoughby discussing the gift of a horse with her sister and saying, "Marianne, the horse is still yours." It can mean only one thing. "From that moment she doubted not of their being engaged to each other." A woman who lets a man speak her name has given him a special power. But it is even rarer for a woman to call a man by his first name. Mr Knightley asks Emma to call him George, but she won't. "Impossible! – I never can call you any thing but 'Mr Knightley'."

Why is Mr Perry getting a carriage?

The plot of Emma turns on Frank Churchill's "blunder" in mentioning the likelihood of Mr Perry, the local apothecary, "setting up his carriage". Frank knows because of his secret correspondence with Jane Fairfax, and is therefore in difficulties when asked by Mrs Weston how he found out. The news is telling. Mr Perry is evidently making so much money from the hypochondriacs of Highbury that he can accede to his wife's desire for a carriage. The Austens themselves owned a carriage for a year or two in the late 1790s but then had to give it up. It would have taken an income of about £1,000 a year to make a carriage affordable, well beyond most genteel households.

Mr Perry can use his carriage to make his lucrative house calls. The "intelligent, gentlemanlike" practitioner is a kind of therapist, whose business is humouring his clucking patients. He is first seen tactfully failing to contradict Mr Woodhouse's absurd opinion that wedding cake is harmful. He agrees that it "might certainly disagree with many – perhaps with most people, unless taken moderately". Though "all the little Perrys" are soon seen "with a slice of Mrs Weston's wedding-cake in their hands". Their father is a man who makes his handsome living from echoing the prejudices of his clients.

Frank Churchill later tries a joke about Mr Perry's earnings, suggesting that if a ball were to be held at the Crown instead of at Randalls there would be less danger of anyone catching a cold. "Mr Perry might have reason to regret the alteration, but nobody else could." Arch-hypochondriac Mr Woodhouse replies "rather warmly", deeply offended at the suggestion that his apothecary relishes minor ailments: "Mr Perry is extremely concerned when any of us are ill." Yet he is getting a carriage because he has battened on the hypochondriacs of Regency England.

Who is wearing mourning?

Lots of people. Near the end of Emma, Mrs Churchill's death makes it possible for Frank Churchill to marry Jane Fairfax. When Frank meets Emma after the announcement of his engagement, he is smiling and laughing on this "most happy day", but suited, we should realise, all in black. We are not told this: Austen's first readers would have "seen" this garb, and registered the clash of official sorrow and private happiness. The deaths of close kin required a period of full (or "deep") mourning – in which clothes were predominantly black – followed by an equal period of "second" or "slight" mourning. Austen's own letters to her sister are full of chat about adapting clothing to mark the death of this or that relative. On hearing of Mrs Churchill's death, Mr Weston shakes his head solemnly while thinking – Austen cannot resist telling us – "that his mourning should be as handsome as possible". His wife, meanwhile, sits "sighing and moralising over her broad hems". Austen's satire is entirely tolerant.

At the end of Mansfield Park, Mary Crawford and Mrs Grant begin a new life together, clad in full mourning because of the death of Dr Grant. Their mourning is not grief. We take it that, even in their black clothes, they are delighted to be rid of an irksome impediment to their sisterly friendship. Austen likes us to notice how official mourners fail to grieve. In Persuasion, Captain Benwick is "in mourning" for Fanny Harville's loss, which means not just that he is sad, but that he is actually wearing black, as the Harvilles are likely to be. Anne learns the story of their shared tragedy, but then their clothes would already have made her curious. If we do not see these clothes we lose something, for Captain Benwick must either eschew his mourning dress while paying his attentions to Louisa Musgrove, or court her while wearing it. Either possibility gives special force to Captain Harville's later exclamation to Anne: "Poor Fanny! she would not have forgotten him so soon." Mourning dress is, after all, donned in order to stop you escaping from the memory of the dead person.

Where does Wickham have a tryst with Georgiana Darcy?

By the seaside – where else? The near-seduction of Mr Darcy's sister is staged with the help of the perfidious ex-governess Mrs Younge at Ramsgate, on the Kent coast, where, we infer, Georgiana Darcy is at Wickham's mercy. Only her brother's last-minute arrival saves her. It is dangerous by the sea. Austen had something particular against Ramsgate, where her sailor brother Francis was stationed in 1803-4. In a letter to Cassandra in 1813 she refers to a friend who has decided to move to Ramsgate and exclaims: "Bad Taste!" In Mansfield Park, Thomas Bertram boastfully describes his flirtatious behaviour in Ramsgate with the younger Miss Sneyd, whoever she be. On arrival in the town, he and Sneyd find "Mrs and the two Miss Sneyds … out on the pier … with others of their acquaintance." "Mrs Sneyd was surrounded by men," he recalls. Sex is in the air in Ramsgate.

Feckless Tom Bertram is a haunter of seaside resorts. Returning from Antigua, he does not dutifully come home to his mother and siblings, but goes to Weymouth. Later in the novel, Julia Bertram accompanies Mr and Mrs Rushworth to Brighton where she meets up with Mr Yates, with whom she elopes. Brighton is truly dangerous. Lydia Bennet meets Wickham there and elopes with him. In Austen's novels, seaside resorts are places for flirtations and engagements, attachments and elopements, love and sex. And honeymoons. In Sense and Sensibility Lucy Steele marries Robert Ferrars and they go on honeymoon to Dawlish in Devon. Emma (who has never seen the sea) and Mr Knightley, once engaged, plan a "fortnight's absence in a tour to the sea-side" following their marriage. You might say that once Emma has truly discovered love she is bound, at last, for the seaside. It will be by the sea that she and Mr Knightley begin a sexual relationship.

Who marries for sex?

Austen's stories rely on an acknowledgment of men's sexual appetites, which explain why that "truth universally acknowledged" – an affluent bachelor's desire for a wife – is in fact true. There are several men in Austen's fiction who "want" a wife for reasons beyond financial calculation. Mr Collins wants one; Charles Musgrove wanted one. The former hoped to please Lady Catherine de Bourgh, but surely had other reasons. The latter, having been turned down by Anne Elliot, rationally opted for her younger sister. We might surmise that a desire for sexual release motivated both "young" men, and that early 19th-century readers would have understood this. In Emma, Mr Elton, the Highbury vicar, is "a young man living alone without liking it". That last phrase carries a weight of meaning. Only a wilfully innocent reader could think that he yearns for a wife just to choose his fabrics and argue with his cook.

Austen's narratives depend on our imagining male sexual needs. Catching us wondering how Mr Palmer in Sense and Sensibility, an intelligent but ill-natured man, could possibly have married a woman as idiotic as Charlotte Jennings, Austen lets Elinor reflect on the puzzle. "His temper might perhaps be a little soured by finding, like many others of his sex, that through some unaccountable bias in favour of beauty, he was the husband of a very silly woman – but she knew that this kind of blunder was too common for any sensible man to be lastingly hurt by it." It is an extraordinary judgment, for Mr Palmer is paired with a fool for the rest of his days. Elinor has seen this happen often. His error has been his yen for "beauty" – or, we might say, "sex appeal". At this stage of the novel, Charlotte Palmer is heavily pregnant (though he is scarcely able to talk to his wife, he does have sex with her). Perhaps her advanced state of pregnancy means a temporary denial of conjugal solace. More reason for his grumpiness.

Why does Robert Ferrars marry Lucy Steele in Sense and Sensibility? All the evidence is for a process of sexual intoxication that Lucy, who has "considerable beauty", manages with great skill. He marries her "speedily" because he wants her. She trades on sexual allure (not mere bluff – we are explicitly told of the "great happiness" of their honeymoon). Mr Bennet's choice of Mrs Bennet has also been sensually determined. In the first chapter of Pride and Prejudice, his joke about his wife not accompanying his daughters to meet Mr Bingley lest he "like you the best of the party" has a hint of ruefulness. As a young man he was "captivated by youth and beauty". Having made his mistake, he must live with it. And after all, we can infer that Mr and Mrs Bennet have carried on an active sex life well into middle age as, "for many years after Lydia's birth", Mrs Bennet is sure that they will eventually have a son.

What does Captain Benwick say in Persuasion?

Nothing worth telling us. There is a special group of Austen characters who may talk and talk, but never get a word of their speech quoted. Captain Benwick is a member. On her first evening in Lyme, Anne gets him for company and finds that, though initially "shy", he has plenty to say, notably about his "taste in reading". Soon he is talking about poetry and repeating the chunks of Scott and Byron that he has got by heart. He has found out the lines that seem to dignify his own love-lorn feelings. Keen to avoid the conversation of Captain Wentworth, Anne spends most of the evening with Captain Benwick. He is full of quotations himself, but says precisely nothing that the author thinks worth quoting.

The next day Captain Benwick seeks Anne out and he is soon talking again, disputing over books. Captain Harville is grateful to her for "making that poor fellow talk so much". The sense is delicately given that Anne is becoming the victim of this previously silent man who has so readily discovered the consolation of talk. As the party walks along the Cobb for a last time before leaving, "Anne found Captain Benwick again drawing near her". He is going to talk and recite some more, but Austen does not tax the reader with what he says. Her heroine's response is charitable: "She gladly gave him all her attention as long as attention was possible." Not enough attention for any of his words to lodge.

It feels like Austen's private joke about a man who recites rather than converses. When Charles Musgrove returns from Lyme he tells Anne about Captain Benwick talking. "'Oh! He talks of you,' cried Charles, 'in such terms ... His head is full of some books that he is reading upon your recommendation, and he wants to talk to you about them ... I overheard him telling Henrietta all about it.'" He keeps being talked about as talking, but his own words are kept from us. So, in some odd way, he never fully exists.

Who has the shortest successful courtship?

Among Austen heroines, it is Catherine Moreland. Northanger Abbey being the shortest of Austen's novels, its love story is also the most rapid. The novel is full of haste – from the progress of Catherine and Isabella's friendship, through John Thorpe's boasts about the speed of his travel, to Colonel Tilney's constant impatience and hurry. (Northanger Abbey has more precise times of day than any other Austen novel.) The time between Catherine's arrival in Bath and her departure from Northanger Abbey is only 11 weeks: a brief acquaintance on which to base a married life together. Briefer still, as during those 11 weeks Henry Tilney has spent some time away at his parish, leaving Catherine at Northanger Abbey with his sister. Having elicited such a speedy proposal from Henry Tilney, Austen reassures us by telling us that he and Catherine in fact marry "within a twelvemonth" of their first meeting – not much less than the year allowed Elizabeth Bennet and Mr Darcy between their first encounter and their nuptials.

Other characters are speedier than Catherine and Henry. Mr Elton, wounded after being rejected by Emma, goes to Bath and writes to Mr Cole just four weeks later to announce his engagement to a woman he had never met before. Charlotte Lucas's notorious advice in Pride and Prejudice is to be as speedy as possible. In order to fix Mr Bingley's intentions, she tells Elizabeth, Jane Bennet "should … make the most of every half-hour in which she can command his attention. When she is secure of him, there will be more leisure for falling in love as much as she chooses." A lengthy courtship has no advantages: "It is better to know as little as possible of the defects of the person with whom you are to pass your life." The shortest courtship imaginable is indeed Mr Collins's of Charlotte, lasting as it does from dinner-time to night-time of a single day, all of it spent in the voluble company of others.

Which novel's plot relies on the weather?

All of them. Austen is a genius with the weather, making it the very principle of chance entering her narratives. Sense and Sensibility is kicked into life by a misjudgment about the weather: Marianne goes walking on the Devon hills with her younger sister Margaret, convincing herself that "the partial sunshine of a showery sky" bodes well. Marianne's "declaration that the day would be lastingly fair" is utter folly, revealed when "a driving rain set full in their face". Fleeing for home, Marianne trips and is rescued by the handsome Willoughby. It might seem a fortunate accident, the beginning of a romance, but Marianne's determination to delude herself about the weather bodes ill.

The weather variously throws lovers together or separates them in each novel, nowhere more decisively than in Emma. Our heroine is contemplating the possible pairing of Mr Knightley and Harriet Smith. The world is narrowing. "A cold stormy rain set in" – unseasonal for July. "The weather affected Mr Woodhouse," requiring Emma ceaselessly to be attentive to him in order to keep him "tolerably comfortable". The evening of rain lengthens out like the long prospect of her future days with only her father for company. But then "the wind changed into a softer quarter; the clouds were carried off; the sun appeared; it was summer again". Mr Knightley arrives and, while Mr Perry consoles Mr Woodhouse for his weather-induced indisposition, he walks with Emma in the garden.

At the critical moment in their conversation, he offers a revelation and Emma declines to know it – she dreads him speaking lovingly of Harriet. They reach the house but she decides to "take another turn". A benign climate blesses their exchange, and he can tell her not that he wishes to marry Harriet, but that he loves her. It is the walk in the sudden fine weather that allows for Mr Knightley's proposal, unpremeditated before he discovers the occasion. The shrewd reader will regard the final betrothal of Emma and Mr Knightley as inevitable, from the moment we know that he is the only person ever to find fault with her. But the best comedy recruits chance, and the lucky change of weather in Emma is there to let us imagine how it might have been otherwise.

• John Mullan's What Matters in Jane Austen? is published by Bloomsbury (£14.99) on 7 June. To order a copy for £9.99 with free UK p&p call 0330 333 6846 or go to theguardian.com/bookshop.