Cracking the agent puzzle was one of the hardest things for me when I was ready to sell my first novel. I did almost everything wrong, and irritated a few people, but in the end, I got lucky. One thing I did right was to sign with the agent who told me he liked my novel, but that it needed rewriting. I've worked with him now for fifteen years.
Here are some of the things that make him a great agent:
1. He returns my phone calls and responds to my emails, usually the same day, never waiting more than twenty-four hours. If you think all agents do that, you should think again.
2. He reads my manuscripts, and suggests improvements. Seems obvious, doesn't it? But there are agents who send things out they haven't looked at at all.
3. He knows the ins and outs of the business, not only the editors and publishers but the arcane stuff like the Google Settlement--inasmuch as anyone can know the Google Settlement.
4. He sends out my work, and follows up with the editors.
5. He thinks of my career and its growth, not just the current sale.
6. He reads my contracts carefully, and negotiates issues with the publishers to make our contracts as favorable to us as possible.
7. He believes in my work, even during the tough times. This is an invaluable boost to my confidence! It doesn't mean he doesn't have criticisms, but that they are always constructive.
8. He's a member of, and active in, the Association of Authors' Representatives, the professional organization that doesn't admit agents who charge reading fees.
9. His associates and assistants all behave professionally, and respond promptly to queries. His website is up to date and easy to navigate.
10. I like him. This is not really a necessary trait, but it makes our long association ever so much more pleasant. This is where I really got lucky. We live on opposite sides of the country, and I couldn't have known we would like each other, but I'm grateful we do.
If you're looking for an agent, a great place to start is the AAR website, at http://www.aaronline.org