If you can get the 2010 version of this book, I highly recommend it. There were tips from individual agents, chapters about querying, and an encyclopedia-like breakdown of agencies, who works at each one, what to send them, how to send it, where to send it, phone numbers--pretty much everything you need and more.

Searching the net for this kind of stuff can be time-consuming. The Guide to Literary Agents does the work for you.

The only reason I didn't give it 5 stars, is be More...

This is a must-have reference for all aspiring authors who's searching for an agent with a polished manuscript. Though outdated, get the latest one in August 2008.

Book is now almost two years old. I recommend a later version.
There is a lot of useful information here.