1. Word of Mouth
The agent search is another situation in which it helps to have a writing community. Share information with others who are going through the process: Who is on their list? Whom have they already contacted? Who gets back quickly? Who just checked into rehab?
And if your writer friends or former professors have agents already, they may offer to put you in touch with them. (See how this played out for another writer through her query letters.)
2. Acknowledgments
Find out who represents authors you admire, either through the acknowledgments in their books, where agents are often thanked, or simply by Googling their names and words like "agent" or "represented by." If they're open to what your literary heroes are doing, they'll probably be open to your work, too.3. Publishers Marketplace
Publisher's Marketplace, an industry newsletter, announces which books have been sold to which presses, and which agent arranged the deal. (For a fee, you may also access an online database of agents and editors.) Read the listings, and take note when a book sounds similar to yours. It also helps to subscribe to Poets and Writers, which periodically interviews agents. If something an agent says resonates with you, consider sending them a query letter.4. Get the Specifics
Once you have a good-sized list of agents, research how to approach them. Not all agents want the same thing from writers. Manus & Associates, for example, wants a query letter and the first 30 pages. Another agency might want the first chapter only. Find out what they prefer and follow their instructions.
To find out what they want, start with their website: most agents offer guidelines for querying them. If they don't, consult a copy of the Guide to Literary Agents, the sister of Novel and Short Story Writer's Market.
For more on the process, see "How to Find an Agent" and the agent FAQs. You can also follow one writer's path to finding an agent.

