How did you narrow the agent market to find the ones you did?
A lot of cross-referencing. I started with Publishers Marketplace (get thyself a subscription stat), and searched for agents who had sold books that I'd loved or who had a lot of success in my genre (women's fic/chick lit). And I flipped through books on my bookshelf to see who I had repped them. (Check the acknowledgements page.) I also hit agentquery.com and searched by agents who repped my genre, THEN went back to PubMktplace to see what deals they'd done. From there, I filtered through everyonewhosanyone.com and writers.net to garner any personal feedback or experience with an agent, and I also googled the agent to see if her name popped up on any articles, interviews, etc. Oh, and of course, went to the agency's website.
I also knew that I (most likely) wanted a woman, that I wanted her to be relatively young (no, I'm not an ageist! I just thought that someone who was my age-ish would better relate to my writing style and the story), whose career was ascending but who wasn't yet a big shot (ergo, I didn't query Binky Urban because I thought I'd get lost on her list), someone who had an established track record of sales (the more sales, the better her contacts, and as I've learned, contacts make up a lot of the game), and someone who, whether through reading her bio or whatever, I thought I might click with.
I'm fortunate in that my agent met (and surpassed) all of the above criteria.