Brush up on your high school algebra and geometry skills. The math problems in the GRE math test require high-school-level math skills. This math level creates an even playing field for everyone who takes the test. The test's main purpose is to gauge problem-solving skills as opposed to judging math skills.
Visit testprepreview.com to work sample problems from the GRE. This website offers assessment tests that allow you to work through problems that are in a similar format to those on the GRE. Answers are included so you can grade yourself.
Take a practice test on GREguide.com. This site offers practice tests in all of the math areas included on the test. These practice tests are presented in the same way they will be presented on the exam.
Download the GRE Practice Book from ETS.org, the company that operates the test (see Resources). This book is filled with information on how to prepare for the test, tips for taking the test and sample questions to help you get a feel for taking the test.