Step 1: Read everything you can about agents in the various sticky threads and FAQ files in Absolute Write.
Step 2: Use search books and/or websites to locate agents who take your genre or books that are similar to your own (the book called "Writer's Market" is one of the most used and can be found in any library).
Step 3: After compiling your list of agents, do research on each agent in the threads in "Bewares and Background Check" (each agent has a thread, see the index at page top). Then look at
P&E. Reject the scammers and the ineffective dabblers.
Step 4: Do research on the reduced list of agents by googling and by talking to current and former clients.
Step 5: Send query letters to the agents on your chosen list.