A few middle-aged couples are chatting at a dinner party when one husband, Harry, starts talking enthusiastically about a new restaurant he has just visited with his wife. What's its name, demands a friend. Harry looks blank. There is an awkward pause. "What are those good-smelling flowers with thorns called again?" he eventually asks. A rose, he is told. "Yes that's it," Harry announces before turning to his wife. "Rose, what's that restaurant we went to the other night?"

It's a vintage joke but it makes a telling point, one that forms the core of a newly published book on memory, Moonwalking with Einstein: The Art and Science of Remembering Everything, by American journalist Joshua Foer. The book, for which Foer received more than $1m in advance royalties in the US, is an analysis of the importance of memorising events and stories in human history; the decline of its role in modern life; and the techniques that we need to adopt to restore the art of remembering.

As Foer points out, we no longer need to remember telephone numbers. Our mobile phones do that for us. We don't recall addresses either. We send emails from computers that store electronic addresses. Nor do we bother to remember multiplication tables. Pocket calculators do the job of multiplying quite nicely. Museums, photographs, the digital media and books also act as storehouses for memories that were once internalised.

As a result, we no longer remember long poems or folk stories by heart, feats of memory that were once the cornerstones of most people's lives. Indeed, society has changed so much that we no longer know what techniques we should employ to remember such lengthy works. We are, quite simply, forgetting how to remember.

Hence Foer's book, which is published by Penguin this month. It outlines the methods that need to be mastered in order to boost our memories and regain the ability to recall long strings of names, numbers or faces. In the process, he adds, we will become more aware of the world about us.

The trick, Foer says, is to adopt a process known as "elaborative encoding", which involves converting information, such as a shopping list, into a series of "engrossing visual images". If you want to remember a list of household objects – gherkins, cottage cheese, sugar and other items – then visualise them in an unforgettable manner, he says. Start by creating an image of a large jar of gherkins standing in the garden. Next to it, imagine a giant tub of cottage cheese – the size of an outdoor pool – and then picture Lady Gaga swimming in it. And so on. Each image should be as bizarre and memorable as possible.

Using methods like this, it becomes possible to achieve great feats of memory quite easily, Foer says. It certainly seems to have worked for him: he won the annual US Memory Championships after learning how to memorise 120 random digits in five minutes; the first and last names of 156 strangers in 15 minutes; and a deck of cards in under two minutes. "What I had really trained my brain to do, as much as to memorise, was to be more mindful and to pay attention to the world around," he says.

These techniques employed by Foer to master his memory were developed by Ed Cooke – a British writer and a world memory championship grandmaster. He acted as Foer's trainer during preparations for the book and helped him achieve his championship performances. "Memory techniques do just one thing: they make information more meaningful to the mind, making the things we try to learn unforgettably bright and amusing," said Cooke.

We remember facts about subjects we are interested in – football or gossip – but day-to-day memories are often devoid of meaning: dates, numbers, definitions or names. These we tend to be poor at recalling. The trick, therefore, is to transform these grey bits of data into something colourful through the use of some energetic imagination.

In this way, all sorts of feats become possible. Arrange the images that you have thought up on a route through a familiar place, like your garden, and imagine yourself passing through that space, said Cooke. Describe each of your created images when you reach its assigned place on your mental route. This way you can talk for an hour while always knowing exactly where you are. "Orators like Cicero used this technique to give seven-hour speeches under intense heckling in the Roman senate," Cooke said.

However, he rejects the idea that people today have simply become sloppy when it comes to using their powers of memory and are now incapable of remembering important facts or bits of information. "The same parts of our minds that we once employed to recall great chunks of data – telephone numbers or addresses or even poems – we use, instead, to remember ways to access information: websites like Google, apps for our iPhones, and routes like that," he said. "In other words, we don't know the data but we remember lots of ways to get at it very quickly."

And in many situations that is a perfectly acceptable way to operate. However, there are several exceptions, he said. "Personally, I like it when doctors remember everything about the human body before they qualify. I don't want to wake up on the operating table to find one of them staring at their iPhones where they have downloaded an app that directs them how to cut up a body.

"And let's face it, there is nothing sadder than someone who has lost their mobile phone and who finds they cannot even phone home or call their parents or partners because they cannot remember a single telephone number. That is an example of the tragic disillusion of personal independence. So, yes, there is a need for us to be able to remember certain things in life."

Further information can be found at Ed Cooke's website: www. memrise.com