Especially if you're new to searching for literary agents. Strauss et al., have posted information that will allow you to avoid the worst aspects of the industry. Their blog is:
At Last! Writer Beware Blogs! A.C. Crispin and Victoria Strauss Reveal All!
On Strauss's blog you'll find warnings about fee-charging agents and more.
Other websites for writers seeking to avoid fee-charging agents:
WRITER BEWARE: http://www.sfwa.org/beware/
PREDITORS & EDITORS: http://anotherealm.com/prededitors/
AGENT RESEARCH & EVALUATION: http://www.agentresearch.com/
JIM FISHER'S USEFUL WEBSITE: http://jimfisher.edinboro.edu/index.html