I grew up at a time when sex–or at least, writing about sex – seemed to be growing up as well. I was 14 when the prosecution of Lady Chatterley’s Lover for obscenity failed. At last, I remember thinking, British literature would be able to catch up with foreign, especially French, literature, which for a century had been far more truth-telling – and far more titillating – than its British equivalent. But having a new freedom and knowing what to do with it were two quite different things. Instead of a blanket prohibition, there was almost the reverse: not just a writerly desire, but a commercial obligation to write in a detailed way about sex. And sometimes all that happened was that the misleading old euphemisms were replaced by the misleading new clichés.

Later, I became a novelist myself, and faced the same questions: how much do you tell/show/imply/elide/omit? What words do you use and what effect are you trying to have? Is writing about sex the same as writing about any other human activity – say, gardening or cricket – or is there a fundamental difference of category? And how is it best done?

There are certainly many different ways of writing badly about sex, from the pornographic to the facetious to the over-solemn. They are bad because they are untrue. Of course, there may in real life be couples who go to bed with one another facetiously, pornographically or with high solemnity, but this is rarely a useful defence. Like many younger readers who had not yet experienced sex – except with myself – I was deeply misled by Lady Chatterley’s Lover, which seemed to insist that running naked though damp under-growth with wild flowers entwined in your pubic hair was just about the closest thing to heaven.

It’s easy to mock, and each generation will mock the previous one because each generation tends to imagine that its attitude to sex strikes just about the right balance; that by comparison its predecessors were prim and embarrassed, its successors sex-obsessed and pornified. And so writing about sex contains an additional anxiety on top of all the usual ones: that the writer might be giving him- or herself away, that readers may conclude, when you describe a sexual act, that it must already have happened to you in pretty much the manner described. This can be a great inhibitor. I remember Kingsley Amis telling me some time in the 1980s that he had recently abandoned a novel because there was a homosexual character in it and he was afraid “the chaps at the club might think I was queer”. This seemed, even at the time, a pitiful excuse, and seems the more pitiful with hindsight.

Self-consciousness leads directly into the question of tone. The more seriously you write about sex, the more you might seem – as sometimes with DH Lawrence – to be writing propaganda for how sex ought to be. Hence the appeal of the comic approach. Make it comic and you will never be accused of solemnity, let alone moralising. And the comic tone inevitably pushes you towards bad sex. It’s hard, perhaps impossible, to be funny about good sex, but with bad sex the field is wide open. That embarrassing premature ejaculation, that humiliating attack of impotence, the wrong underpants, the social uncertainty of what and where and when and how and how often. This is safe territory for the novelist – perhaps too safe.

Vocabulary is the next concern. How far do you go with the naming of parts, which parts do you name, and what names do you give them? At the basic level, he put his what into her – or indeed his – what? The range of terms on offer begins with the medical, and runs through the objectively descriptive, the childish, the vernacular and the coarse to the very coarse. Where between the Latinate and the Anglo-Saxon do you pitch it? And/or do you, or your narrator, divert into metaphor and poeticism, search for the enlivening comparison? There are new dangers here. John Updike is a writer whom I revere, and who wrote with precision and understanding about sex, especially from the male point of view; but in one novel – I think it was Brazil – he kept comparing the male member – as he wouldn’t have called it – to a yam. Whenever he did so, instead of my visualising all the more clearly the sex that just was about to happen, I kept imagining a vegetable stall.

The proper, grown-up novel is the most intimate of art-forms, the one that puts the reader’s mind and heart most closely in touch with the minds and hearts of the characters; it is the place where the most truth about the intimacies of life can, and should, still be told. So when writing a sex scene, I first try to discard any self-consciousness about what others might conclude. I work out where on the sliding scale between laughter and seriousness I want the activity to take place. What is the level of trustingness, and on whose side does power lie? How does what happens between the sheets reflect the relationship between these characters when they are fully dressed? What words would such characters use between themselves, if indeed they use any? Whose point of view do I want it seen from, and what consequences might it have for the plot? Then I try as best I can to describe an activity that encompasses both utter freedom and necessary control; and which, in this last respect, has surprising parallels to something else – the act of writing.

So yes, sex is quite a bit more complicated than gardening or cricket. But however well you might do it – the writing, I mean – you should always expect to be laughed at by subsequent generations. And – in any case – to hell with the chaps at the club.

The Essay: Explaining the Explicit is on all this week at 10:45pm on Radio 3