I wrote these 25 commandments as a panic response 15 or more years ago to an invitation to do some media training for a group of Elsevier editors. I began compiling them because I had just asked myself what was the most important thing to remember about writing a story, and the answer came back loud and clear: "To make somebody read it."

Ultimately, there's no other reason for writing. Journalists write to support democracy, sustain truth, salute justice, justify expenses, see the world and make a living, but to satisfactorily do any of these things you have to have readers. Fairness and accuracy are of course profoundly important. Without them, you aren't in journalism proper: you are playing some other game. But above all, you have to be read, or you aren't in journalism at all.

I wrote down what was in my mind and once I'd started numbering things, I had to go on. I got past 10, and then 20, and stopped guiltily at 25. I then didn't have time to reduce the text to a formal Ten Commandments. The 25 things got distributed among the Elsevier editors the next morning and then some time later I got asked to talk to some staff at Nature, so I used the same set of prompts, and one or two people asked me for copies.

I gave it the not-very-serious subtitle of "manifesto for the simple scribe" and at around the same time, I realised that when stories that I had tried to write turned out wrong, it was because I'd broken one of my own rules. So I decided I might have written something quite useful, after all.

1. When you sit down to write, there is only one important person in your life. This is someone you will never meet, called a reader.

2. You are not writing to impress the scientist you have just interviewed, nor the professor who got you through your degree, nor the editor who foolishly turned you down, or the rather dishy person you just met at a party and told you were a writer. Or even your mother. You are writing to impress someone hanging from a strap in the tube between Parson's Green and Putney, who will stop reading in a fifth of a second, given a chance.

3. So the first sentence you write will be the most important sentence in your life, and so will the second, and the third. This is because, although you – an employee, an apostle or an apologist – may feel obliged to write, nobody has ever felt obliged to read.

4. Journalism is important. It must never, however, be full of its own self-importance. Nothing sends a reader scurrying to the crossword, or the racing column, faster than pomposity. Therefore simple words, clear ideas and short sentences are vital in all storytelling. So is a sense of irreverence.

5. Here is a thing to carve in pokerwork and hang over your typewriter. "No one will ever complain because you have made something too easy to understand."

6. And here is another thing to remember every time you sit down at the keyboard: a little sign that says "Nobody has to read this crap."

7. If in doubt, assume the reader knows nothing. However, never make the mistake of assuming that the reader is stupid. The classic error in journalism is to overestimate what the reader knows and underestimate the reader's intelligence.

8. Life is complicated, but journalism cannot be complicated. It is precisely because issues – medicine, politics, accountancy, the rules of Mornington Crescent – are complicated that readers turn to the Guardian, or the BBC, or the Lancet, or my old papers Fish Selling and Self Service Times, expecting to have them made simple.

9. So if an issue is tangled like a plate of spaghetti, then regard your story as just one strand of spaghetti, carefully drawn from the whole. Ideally with the oil, garlic and tomato sauce adhering to it. The reader will be grateful for being given the simple part, not the complicated whole. That is because (a) the reader knows life is complicated, but is grateful to have at least one strand explained clearly, and (b) because nobody ever reads stories that say "What follows is inexplicably complicated ..."

10. So here is a rule. A story will only ever say one big thing. If (for example, and you are feeling very brave) you have to deal with four strands of a tale, make the intertwining of those four strands the one big thing you have to say. You may put twiddly bits into your story, but only if you can do so without departing from the one linear narrative you have chosen.

11. Here is an observation. Don't even start writing till you have decided what the one big thing is going to be, and then say it to yourself in just one sentence. Then ask yourself whether you could imagine your mother listening to this sentence for longer than a microsecond before she reaches for the ironing. Should you try to sell an editor an idea for an article, you will get about the same level of attention, so pay attention to this sentence. It is often – not always, but often – the first sentence of your article anyway.

12. There is always an ideal first sentence – an intro, a way in – for any article. It really helps to think of this one before you start writing, because you will discover that the subsequent sentences write themselves, very quickly. This is not evidence that you are glib, facile, shallow or slick. Or even gifted. It merely means you hit the right first sentence.

13. Words like shallow, facile, glib and slick are not insults to a journalist. The whole point of paying for a newspaper is that you want information that slides down easily and quickly, without footnotes, obscure references and footnotes to footnotes.

14. Words like "sensational" and "trivial" are not insults to a journalist. You read what you read – Elizabethan plays, Russian novels, French comic strips, American thrillers – because something in them appeals to your sense of excitement, humour, romance or irony. Good journalism should give you the sensation of humour, excitement, poignancy or piquancy. Trivial is a favourite insult administered by scholars. But even they became interested in their subject in the first place because they were attracted by something gleaming, flashy and – yes, trivial.

15. Words have meanings. Respect those meanings. Get radical and look them up in the dictionary, find out where they have been. Then use them properly. Don't flaunt authority by flouting your ignorance. Don't whatever you do go down a hard road to hoe, without asking yourself how you would hoe a road. Or for that matter, a roe.

16. Clichés are, in the newspaper classic instruction, to be avoided like the plague. Except when they are the right cliché. You'd be surprised how useful a cliché can be, used judiciously. This is because the thing about journalism is that you don't have to be ever so clever but you do have to be ever so quick.

17. Metaphors are great. Just don't choose loopy metaphors, and never, never mix them. Subs on the Guardian used to have a special Muzzled Piranha Award, a kind of Oscar of incompetence, handed to an industrial relations reporter who warned the world that the Trades Union Congress wildcats were lurking in the undergrowth, ready to dart out like piranhas, unless they were muzzled. George Orwell reports on the case of an MP who claimed that the jackbooted fascist octopus had sung its swansong.

18. Beware of street cred. When Moses ordered his commanders to slay the Midianites he wasn't doing it to show that he was well hard. When he warned Pharaoh to let his people go he wasn't saying "give us room to breathe, man, and Pharaoh's, like, no way feller!" The language of the pub or the café has its own rhythms, its own body language, its own signalling devices. The language of the page has no accent, no helpful signalling tone of irony or comedy or self-mockery. It must be straight, clear and vivid. And to be straight and vivid, it must follow the received grammar.

19. Beware of long and preposterous words. Beware of jargon. If you are a science writer this is doubly important. If you are a science writer, you occasionally have to bandy words that no ordinary human ever uses, like phenotype, mitochondrion, cosmic inflation, Gaussian distribution and isostasy. So you really don't want to be effulgent or felicitous as well. You could just try being bright and happy.

20. English is better than Latin. You don't exterminate, you kill. You don't salivate, you drool. You don't conflagrate, you burn. Moses did not say to Pharaoh: "The consequence of non-release of one particular subject ethnic population could result ultimately in some kind of algal manifestation in the main river basin, with unforeseen outcomes for flora and fauna, not excluding consumer services." He said "the waters which are in the river ... shall be turned to blood, and the fish that is in the river shall die, and the river shall stink."

21. Remember that people will always respond to something close to them. Concerned citizens of south London should care more about economic reform in Surinam than about Millwall's fate on Saturday, but mostly they don't. Accept it. On 24 November 1963, the Hull Daily Mail sent me in search of a Hull angle on the assassination of President Kennedy. Once I had found a line that began "Hull citizens were in mourning today as …" we could get on with reporting what happened in Dallas.

22. Read. Read lots of different things. Read the King James Bible, and Dickens, and poems by Shelley, and Marvel Comics and thrillers by Chester Himes and Dashiell Hammett. Look at the astonishing things you can do with words. Note the way they can conjure up whole worlds in the space of half a page.

23. Beware of all definitives. The last horse trough in Surrey will turn out not even to be the last horse trough in Godalming. There will almost always be someone who turns out to be bigger, faster, older, earlier, richer or more nauseating than the candidate to whom you have just awarded a superlative. Save yourself the bother: "One of the first ..." will usually save the moment. If not, then at least qualify it: "According to the Guinness Book of Records ..." "The Sunday Times Rich List ..." and so on.

24. There are things that good taste and the law will simply not let you say in print. My current favourites are "Murderer acquitted" and (in a report of an Easter religious play) "Paul Myers, who played Jesus Christ, emerged as the star of the show." Try and work out which one has the taste problem, and which one will cost you approximately half a million per word.

25. Writers have a responsibility, not just in law. So aim for the truth. If that's elusive, and it often is, at least aim for fairness, the awareness that there is always another side to the story. Beware of all claims to objectivity. This one is the dodgiest of all. You may report that the Royal Society says that genetic modification is a good thing, and that depleted uranium is mostly harmless. But you should remember that genetic modification was invented by people who were immediately elected to the Royal Society for their cleverness, by people already in there because they knew how to enrich uranium fuel rods and deplete the rest. So to paraphrase Miss Mandy Rice-Davies (1963) "They would say that, wouldn't they?"

Tim Radford will be talking about his career tonight in conversation with Alok Jha at Imperial College London, 6-7pm

• This article was amended on 21 January 2011. The original referred to Dashiel Hammet. This has been corrected.