While Miss Snark advises her devoted Snarkings to query widely when looking for that special agent, she also recommends you research, research, research before you draft that "Dear Agent" letter.
Don't be one of those people who queries a literary agent just because you like the agency's moniker or they have a nice website. (Although, I do love the name Harvey Klinger. Fortunately it's a great agency that reps YA.) They've got to be more than just a pretty facade.
If you've written the mother of all fantasies, don't query a crime-lovin' agent just because they sold one fantasy novel in 1989. The reason they may have had that sale is because a client who normally writes crime saddled them with their one and only 1,000-page fantasy novel and by some fluke it struck gold.
You want to find out what projects the agent would climb Everest in stilettos for. Or more specifically, you want an agent who knows the market and loves your genre. You want to know how they operate and who their clients are. So how do you know what an agent wants if you don't exactly get invited to all the good publishing parties?
There are some terrific resources on the Net to help you find a good match these days. And I don't mean rsvp.com.au. AgentQuery, AAR, Absolute Write, Preditors & Editors, Publishers Marketplace, agent blogs, writer blogs, etc, all give you vital clues. But also sniff out interviews, where you'll get more than the usual brief bullet points on what an agent likes/dislikes.
I found these great interviews by Googling agents' names + the word interview. Thanks go to the people who actually conducted and posted these interviews. Take a good look around their sites for more useful info.
Michael Neff's interview with Maya Rock of Writers House.
Gawker's interview with Ginger Clark of Curtis Brown, New York.
Alma Fullerton's interview with Nathan Bransford of Curtis Brown, San Francisco.
K.L. Goings's interview with Ginger Knowlton of Curtis Brown, New York. (Yes, there are two Gingers at CB, and they're both lovely.
Stephanie Rowe's interview with Irene Goodman of the Irene Goodman Literary Agency.
Gena Showalter's interview with Nephele Tempest of The Knight Agency. (Bless you, Ms. Showalter, for giving the pronunciation of Nephele! I'd always wondered...)