Choosing your subject

You can't choose your relatives but you can choose which ones you write about. Deciding on whose lives you will research - whether as part of a family history or as a single biography - will depend on several factors. Ideally, your interests and skills should match theirs. If you want to write about a Nobel Prize winning economist but you failed maths GCSE you may struggle to appreciate their work. On the other hand, ignorance can be the ideal starting point from which to demystify a complicated subject.

Weigh up the type and availability of sources before choosing your subject. There should be enough material to allow you to get to know the person you're researching but not so much that it would take you your lifetime to read it. When Michael Holroyd was researching the life of George Bernard Shaw he began to think that Shaw, who wrote 10 letters every day of his adult life and had the benefit of shorthand and secretaries, could write more in a day than Holroyd could read. By contrast, if you're interested in an early professional footballer you may discover that he didn't write a single letter and you will have to find other ways of giving him a "voice" - perhaps by quoting from newspaper interviews or speaking to someone who knew him.

Much research can be carried out on the internet but you will still have to interview people, consult collections and probably make at least one trip to somewhere such as the National Archives (formerly the Public Record Office) in Kew or the Imperial War Museum in south London. How far you live from your main sources will affect the time and expense involved. If they are abroad both will rise and you may also face language difficulties.

Copyright

If you intend to quote extensively from a particular source don't wait until the last minute to see whether you will be granted permission. You may be refused or the price might be prohibitively high - in which case you will have to rewrite the book. The use of song lyrics, even if you want to use just one line, can be particularly expensive.

You can't quote a "substantial" part of a copyright work without permission but what constitutes "substantial" is open to debate. Four lines from a short poem might be "substantial", whereas several sentences from a novel would not be.

Letters belong to the recipient but the writer holds the copyright which is passed to their estate after their death. When travel writer Paul Theroux wrote a memoir about his one time friend, Nobel Laureate VS Naipaul he was only allowed to quote tiny amounts from Naipaul's letters to him and was not allowed to see his replies. He was, in effect, denied access to his own letters.

Whether a work is still in copyright depends on factors such as when the author died and their nationality. Most archives should be able to advise you on how to ask for permission to use material they hold or you can write to the publisher of a writer you want to quote. The Society of Authors publishes two useful guides: Copyright and Moral Rights and Permissions.

What's out there already?

· Consult the British Library catalogue to see if any books have already been written about the person or topic you're interested in; check when they were written and who published them. If they appeared a long time ago or were published by a specialist press you have a greater chance of interesting a publisher in a new account.

· Do an online search for the name of the person you're interested in and make a note of sources to follow up, for example, archives, academic publications or appreciation societies.

· Check an online bookseller such as Amazon.com to see if any books about your subject are due to be published.

· If you want reassurance that no one else is working on the same subject contact the main sources or experts - for example, family members, copyright holders of material such as letters or diaries, or archivists - who may know. However, this is not foolproof and carries the risk of alerting a biographer in search of a subject.

Is my idea commercial?

If you want to get published consider how commercial your idea is before you devote the next few years of your life to it. Your grandchildren will probably enjoy reading your account of how their great-aunts and uncles survived in the poverty of 1930s Ireland because of their personal connection to the people you're describing. But the book is likely to be too similar to Frank McCourt's Pulitzer Prize-winning, Angela's Ashes to interest a publisher.

Likewise, finding a publisher for a biography of a well-known person is very difficult unless you have something new to say. Most publishers would be reluctant to commission a new biography of someone like Winston Churchill. However, if your father was Churchill's driver and kept a diary of his working life they might be interested in an account told from the chauffeur's perspective. Alison Light took a startlingly fresh approach to the Bloomsbury Set - a group which had been written about exhaustively and exhaustingly - in her book, Mrs Woolf & the Servants, The Hidden Heart of Domestic Service.

Conversely, "sales and marketing" (who have a huge say in whether a publisher commissions a book) are likely to be wary of a subject that no one has heard of. However, there are plenty of examples of individuals dragged out of obscurity to delight modern readers. Kate Summerscale became fascinated by Joe Carstairs when she wrote her obituary for the Daily Telegraph. When she started work on her biography very few people had heard of Carstairs, an oil heiress who dressed like a man, held records for speedboat racing in the 1920s, owned her own island and poured her affection into a rag doll. Summerscale told her story in such a compelling way that The Queen of Whale Cay became a bestseller.

Sometimes the quality of the writing is enough to secure publication. On paper Bad Blood by Lorna Sage, a memoir written by an academic about growing up in the 1940s in a bleak vicarage on the English/Welsh borders, may not sound compelling but it won the Whitbread Biography of the Year in 2001 and was praised for its lyrical writing and dark humour.