My sources say that agents place 65 to 75 percent of their books. Beware of those who claim higher numbers. Agents receive 15 percent of your royalty. Unless it's negotiated differently, publishers send the royalty check and statements to the agent. The agent is responsible to ensure the accuracy of the accounting figures.
My current agent has challenged those figures several times and won. It wasn't an issue of publisher dishonesty, but lack of understanding or ignorance. Every contract is different and sometimes the details get lost.
So how do you get an agent?
Find out who they are through writers loops; attend writers conferences; check web sites, or see Sally Stuart's The Christian Writers Market Guide, an annual publication. Writer's Digest puts out their Writers Market Guide each year. Most libraries carry the Literary Marketplace (known as LMP) in their reference section. Ask your friends who have agents. The AAR—Association of Authors' Representatives— is a voluntary organization of agents who subscribe to a code of ethics. They have an excellent website: http://aaronline.org/.
Here's another tip. When I read books by authors I like, I read the acknowledgments and they often credit their literary agent. That's another solid lead. It implies that the agent likes that type of book and might be open to authors in the same genre.
Before you start your search for an agent, make sure that your manuscript is the best you can make it. It's worth the money to pay an editor or a proofreader or both. The manuscript may look fine to you, but to a professional, it may not.
Before you seek a literary agent,
be sure you're ready for one.