I finished my novel, and everyone I've talked to says I need an agent. How do I find one?
Try and find a list of agents who write in your genre. Check out their websites! Find out if they are accepting new clients. If they aren't, then check out another agent. But if they are, try sending them a few chapters from your story, a brief, and a short cover letter asking them to represent you.
In the cover letter mention your previous publication credits. If sent via post, then I suggest you give them a means of reply, whether it be an email or a stamped, addressed envelope.
Agents will try their best to improve your chances of getting a book published.
I have to add a few things to Randomman's answer:
- If you have that list, check if the agents are reputable! Google them. There are a lot of black sheep out there.
- Go to the homepage of authors of the same category you write in. Some are mentioning their agents.
- Follow Vatine's advice in his comment to Randomman's answer. If you do not find a guideline, do not send anything to them without asking. First write an email and ask for permission, if they are interested in your stuff.
- If they have no formatting guidelines, look up the industry standard, how your sample chapter and synopsis should be formatted. (In Germany it's the maximum of 30 lines a page with 60 characters each line in Courier, but that could differ in your country.)
This may not be an exact answer to your question, but:
Don't forget that you don't always need an agent (in fact, depending on the agent and your situation, it can be a lot worse than having no agent).
You need to read a bit about what exactly an agent can do for you and decide what kind of agent you want to hire.
Also be aware that some "agents" advertising on line are 100% scam ("hey, I can make you a star, pay me an up-front fee!" then nothing).
There is a lot of good info out there from very experienced authors, especially two articles by Dean Wesley Smith:
http://www.deanwesleysmith.com/?p=720 (this is the second one, but the other is linked in it)
And this Writing Excuses podcast:
I seem to recall that either Writers Digest or Writers Market keeps a list you can subscribe to of agents, what genres they work in, query guidelines, etc.
Do not use lists of agents, especially not the ones you find on the web. You don't know how the agents get on that list and will have a hard time finding out if they are good.
Instead look at the published books in your genre, make a list of their authors, and then find out who represents them. That way you will know that those agents are successful – and you want to be the client of an able agent.
Only if these agents have rejected you, or if for some reason you cannot find any agents in this way, would I resort to the lists mentioned in some of the other answers.