1. You are happy with the first 10,000 words.
10,000 words is the bare minimum an agent will require, and the chapters should be in consecutive order (not extracted from later sections of the novel).
2. You know where the novel is going.
You don't need to have the whole thing written (although some agents prefer it if you have), but you must provide a clear indication of where it is going in your 500 word synopsis. So try and avoid adding teaser questions like 'who is the mysterious stranger from the heroine's past?' Or - if you do ask questions like that - make them rhetorical, and answer them in the next sentence.
3. You've got the presentation right.
Double-spaced text on good quality white printing paper, and no gimmicks like multi-coloured bulldog clips or a picture on the front sheet.
4. You've checked your diary.
If an agent likes it they'll either ask to see the whole thing, or want you to meet them - normally within a few days of their phonecall. So don't send your novel off if you're just about to go on a three week holiday in Barbados (unless of course the agent lives in Barbados, which is unlikely).
5. Grammar/spelling.
Arguably THE most important thing to check. I've said it before and I'll say it again - if an agent spots a glaring error on the first page, you've just provided your manuscript with a short-cut to the wastepaper basket.
6. You're sending to the right agent.
As well as checking The Writer's and Artist's Handbook for a suitable agent, you should also do some research on Google. If possible try and find out who represents your favourite authors, or people who write books in the same genre, as these will be obvious agents to contact.
7. You've got a back-up.
Don't depend on just one agent - make sure you know who else to send to, in case it is rejected. It's simple mathematics - the more agents you send to, the better the odds.
8. You've been objective.
Try and read your novel as if it was written by someone else. Imagine yourself in a bookshop picking up the novel and reading the first few pages. This will help you to work out if it is there yet.
9. You've got a good covering letter.
For 'good' read 'short'. Describe your novel in about two sentences, and keep your description of yourself as brief as possible.
10. You've got the right attitude.
Sending to agents is kind of like going on a blind date - just because you don't hit it off with the first agent you send to, doesn't mean you're never going to find one. It just means you might have to change your strategy a little. But don't take it too personally.......
Ten things to check before you send your novel to an agent