I entirely agree with karenw911. Any real LSAT will help. But, hey, you're going to be paying hundreds of dollars for the LSAT, LSDAS, and application fees, and tens of thousands for law school - so why not spend $20 or $30 and buy a couple of books?
I highly recommend any of the 10 actual, complete LSATS books
Kaplan LSAT 180 - this book REALLY helped me. It drills you on the toughest questions.