Take the sample test for private pilot

http://www.sportys.com/faatest2/default.cfm

This will let you do a sample run of 60 questions, time you, grade you, and then let you see all the right/wrong questions and answers. Also, all the needed materials are available (you don't need your own private copy of booklet FAA-CT-8080-2E of your very own.. but.. it helps).