We suggest the following steps:

• Read about the format of the GMAT exam on mba.com.
• Download and use the free GMATPrep® test-preparation software so you can become familiar with the format used in computer-based testing.
• Review the types of questions on the GMAT exam by looking at sample questions for each section of the test. (Read the mba.com articles on the Analytical Writing Assessment section, Verbal section, and Quantitative section.)
• To study for the Analytical Writing Assessment (AWA) section of the GMAT exam, practice writing an essay using the AWA Topics available on mba.com, or you can purchase GMAT Write—a software designed to help you practice your essay writing skills. GMAT Write will grade your essay using the same technology that the actual exam uses.
• Purchase a set of three GMAT Paper Tests for extra practice.
• Depending on how long it has been since you studied math, you may want to do a review of basic math skills.
• If you want more sample questions to study, you can buy Official Guide for GMAT Review, 12th Edition, the Official Guide for GMAT Verbal Review, 2nd Edition, or the Official Guide for GMAT Quantitative Review, 2nd Edition. Each Guide has hundreds of real GMAT questions, answers, and explanations.
• Review and study one section of the test at a time.
• Read the articles under the heading "Test Day" to find out what you will need to bring to the test and what you should expect at the test center.
• Allow for at least four weeks of studying before you take the test.

Remember, the best thing you can do for yourself is arrive prepared on test day.