As long as you didn't mess something up horribly, you should get pages and pages of results -- most likely from agency websites. Obviously, check out the links and read up on what the agents are interested in, and what agent there seems like the closest match for you and your book.
You can also look up agents in books like The Jeff Herman Guide to Editors, Publishers, and Literary Agents, Publisher's Marketplace, and so on.
A lot of agents are starting their own blogs, where you can get a feel for the agent's personality, what kind of books they're looking for, and news on the industry in general.
Lastly, I have a few places on the Internet that I've stumbled upon, which also feature lists of agents. Some of them -- like Casey McCormick's blog, Literary Rambles -- are updated and added to regularly, and some of them...not so much. Still, they've been helpful to me, and that'll hopefully be true for you, too.
- Agentquery, which automatically filters out agents based on the genre you select
- 1000 Literary Agents
- Literary Rambles (mentioned above, remember?)
- The Guide to Literary Agents is also helpful, especially the agent interviews
The place to check credibility is Preditors & Editors, which lists agents as well.
There you have it. There are other places, of course, tons and tons of them. But it's up to you to go out and find them. Have any others that you think should be listed? Mention them below in the comments.