Ditto all the above.
My own standard route:
-- Agent Query and Query Tracker to make up preliminary lists of agents who accept my genre. From these, I extract the basic information for my database.
-- On to Publisher's Marketplace for more detailed information. At some point, you'll find a subscription to this resource very useful, even if only for a couple months.
-- On to the agent's or agency's own site. If there's a conflict of information between the agent's site and other sites, I go with the agent's site.
-- On to AW and Bewares and Recs.
Now my database is packed with info, and I'm ready to make my own ranking of the agents based on what I have to offer and what the agents seem to offer and prefer and how sturdy their sales records are.
Lots of work? Hell, yes. Making my ranked database was a part-time job for several months. But learning to be a professional isn't supposed to be easy.