These rules (below) are from Hilary Mantel, winner of the Man Booker prize for her historical novel Wolf Hall (which I haven't read yet, but have heard people raving about), and her thoughts really struck a chord with me. I especially liked: Write the book you'd like to read. (Although I have to admit I'd be writing single title if I followed that suggestion to the letter). Hmmm... food for thought.
You can read the other writers' rules here.
1 Are you serious about this? Then get an accountant.
3 Write a book you'd like to read. If you wouldn't read it, why would anybody else? Don't write for a perceived audience or market. It may well have vanished by the time your book's ready.
4 If you have a good story idea, don't assume it must form a prose narrative. It may work better as a play, a screenplay or a poem. Be flexible.
5 Be aware that anything that appears before "Chapter One" may be skipped. Don't put your vital clue there.
6 First paragraphs can often be struck out. Are you performing a haka, or just shuffling your feet?
7 Concentrate your narrative energy on the point of change. This is especially important for historical fiction. When your character is new to a place, or things alter around them, that's the point to step back and fill in the details of their world. People don't notice their everyday surroundings and daily routine, so when writers describe them it can sound as if they're trying too hard to instruct the reader.
8 Description must work for its place. It can't be simply ornamental. It usually works best if it has a human element; it is more effective if it comes from an implied viewpoint, rather than from the eye of God. If description is coloured by the viewpoint of the character who is doing the noticing, it becomes, in effect, part of character definition and part of the action.
9 If you get stuck, get away from your desk. Take a walk, take a bath, go to sleep, make a pie, draw, listen to music, meditate, exercise; whatever you do, don't just stick there scowling at the problem. But don't make telephone calls or go to a party; if you do, other people's words will pour in where your lost words should be. Open a gap for them, create a space. Be patient.
10 Be ready for anything. Each new story has different demands and may throw up reasons to break these and all other rules. Except number one: you can't give your soul to literature if you're thinking about income tax.