I was sitting on a bench beside the River Cocker one day this summer, filling in time waiting for someone, and idly watching the ducks, when an elderly woman came and sat down beside me and began to talk as though she had known me all her life.

Within 10 minutes I was intimately acquainted with her childhood in Bolton, her marriage to a soldier who came from Cockermouth, her move up to Cumberland, her two miscarriages, the death of her husband, the death of her brother’s first wife, his second marriage to a woman of whom she did not approveIriveting. I loved it all.

Whenever there was the slightest pause in this virtual stream of consciousness, I prodded her on. “And then?” I urged. “And then what happened?” At the end of half an hour, she got up to go. She was on her way to a Fellowship meeting at her church. She said it had been nice talking to me. I said it had been fascinating listening to her. “Oh, I know,” she said, “I’ve had an interesting life. I should write a book about it, and I might, I might write my memoirs one day.” And she walked off, laughing.

So far as I could tell, she had, in fact, not had an interesting life at all, though I’d meant it when I’d said I was fascinated, because anyone’s life story fascinates me. She’d had a very ordinary life as a housewife with no children. But so far as she was concerned, her life had been full of drama and she would like to write a book about it.

It’s a statement heard so often - “Oh, I could write a book about my life”, said with absolute confidence and the inference that the only problem is lack of time and opportunity. Put to the test, few would pass it, and yet the memoir is the most accessible and obvious form for a book to take. The material is all there in the head - no plot has to be thought of, no characters invented, no background imagined. All that needs to be done is to let it all out, get it all down on paper.

But that is not all that has to be done, of course. Memories alone, however vivid, don’t make a book. A mass of memories has no shape to it, no form. In the memoir, structure is all. Discipline is more essential than in almost any other kind of writing because memories are so very unruly, humping about all over the place in the most unreliable fashion. They don’t, however fulsome, lead anywhere. They need to be formed into a meaningful pattern in the same way that a length of material has to be cut out before it can be sewn up in to a dress. You can’t just wrap the material around you and say “There, a dress” - or, if you do, you’ll fool nobody.

Yet this imposing of a pattern is not as difficult as it sounds. The structure, after all, is readily available. There is an actual place to start. Everyone is born, everyone has a mother and a father to start them off (or until recently they did). It can feel most satisfactory to the aspiring memoir writer to know how to begin but what can quickly surprise them is having to acknowledge that this beginning isn’t really a beginning at all. Starting means going backwards, not forwards.

This is the point at which to apply for a birth certificate, if it isn’t already to hand, and study it carefully. It will provide all kinds of information about parents and place of birth and from this, other certificates can be sent for and parish registers looked at. Even if the birth certificate is a short one, with no father’s name, that in itself will tell you something. Your birthplace provides a framework for the early chapters. The power of place, is very important in a memoir. Everyone recalls their first impression of place and describing it in detail trains the memoir writer to be precise.

Schooling is the next marker. Most people effortlessly remember names of teachers and classmates, the lessons they loved and those they hated, the playground games and fights. Here the danger is of merely compiling a list and so, selection has to come into the memoir for the first time. The important thing is not to write all this as a record but to try to get back inside the mind and emotions of the schoolchild you were. A memoir, to have any resonance, has to be about feelings, not just facts. The facts might be entertaining or shocking, but without communicating the feelings behind them they will fall flat.

People often aren’t sure about what they felt so long ago, or they are hesitant about confessing. But it is this diffidence a memoir needs to give it the ring of truth and there should be no embarrassment about showing it. The words “I can’t quite remember” should occur quite regularly or else everything will seem too neat and therefore suspect. This is especially true where conversations are reproduced. Who can claim to reconstruct the dialogue of many years ago with any degree of accuracy? It’s best to admit this and stick to reported speech, where all kinds of liberties with the truth can be taken.

It is hard, too, to be precise all the time about dates. But the reader is not going to care whether some incident happened in June or July, in the morning or the afternoon. Some chronology is essential, but there’s no need to get bogged down in it and panic because you can’t establish whether one event happened before or after another. Nor should there be a determination to go through every single year of your life - everyone knows that sometimes two weeks in one particular year is of huge significance and a whole other decade of very little. Focus on the significant and skim the rest. And that is the real trick about writing a memoir: selecting what seems to have been significant and concentrating on this once the basic structure is in place.

Sometimes the easiest way to do this is not chronologically but thematically. Chapters can be devoted to houses lived in, or jobs, or clothes worn, or holidays, or sport. A life can develop quite smoothly done like this instead of unrolling rather drearily in a strict chronology. Themes offer constant variation and lead the writer to set the memoir in a wider context which gives it more depth.

Approaching your life like this can also lead to some simple but rewarding research. People are awed by the word “research” but it is only a matter of satisfying curiosity and checking things and it is easy to do. Every town has a local history archive; access to it is simple. Librarians, on the whole, are not intimidating and only too pleased to have their libraries and archives consulted. It can be thrilling looking up old newspapers, for example, seeing how your memories of an event or a person match up with what may have been reported. This kind of thing can become compulsive, so watch out.

The question of publication isn’t necessarily depressing. At the moment, publishers are keen on memoirs but even so, it is true that the chances of a first-time author finding a mainstream publisher are slim - though not hopeless. Look round a bookshop, find a memoir that you think comes nearest to the sort of book you feel you’ve written, then send your typescript to the publisher of it with a letter saying what your memoir covers.

Rejection is probable, but then you move on to the alternatives. These days there are many small publishing firms who will publish memoirs by local people (again, look round your bookshop). These firms won’t pay you an advance but will agree to pay a percentage of any sales, so although you may not make any money, you will see your memoir published. If that fails, self-publishing is far better than vanity publishing (when you pay the publisher). Take your typescript to the printers, ask for a quote for 1,000 copies. If you’ll settle for a stapled book, not a perfectly-bound one, a soft not a hard cover, then this can cost as little as Pounds 2,000 (depending on the length) and you could get most of that back if you sell only half the copies. It will be up to you to find places to sell your memoir but outlets can be found. The Lake District Book of the Year Prize this year had winners in two categories who had done exactly this.

But maybe publication matters less to the memoir writer than any other. Just doing it, finally writing that book everyone is reputed to have in them, may prove satisfying enough. Seeing it written down and there for the family to read can feel like a mission completed and give great pleasure. Why want more?

* Margaret Forster’s own memoir Hidden Lives is published by Viking and is available in Penguin at Pounds 6.99.

* The Arvon Foundation runs highly respected creative writing courses at centres in Devon, Yorkshire and Scotland. The first 10 readers to send a TES masthead together with their address to David Pease at The Arvon Foundation, Lumb Bank, Heptonstall, West Yorkshire HX7 6DF will receive the new Arvon brochure in January and 20 per cent off the course of their choice.