Understand scoring methods that the GRE uses. If you answer the first questions in each section correctly, you must complete harder questions, but can get a higher score because you are given access to the hardest questions with the highest point values. Answering them incorrectly means you then receive easier questions with lower point values. Answering questions correctly early on in the test can have a large impact on your final score.
Become familiar with what the GRE test expects from test-takers. Skills you should brush up on should help with the analytical writing, verbal reasoning and quantitative reasoning sections. The test is three hours, not including the unscored research section, which means that you need to focus on increasing your speed and accuracy while improving your general knowledge in these areas.
Review notebooks and tests from classes you took in college, while also studying books at the library. Highlight important parts that you might see again. This gives you a broad knowledge of facts and skills that can help you do well on the GRE.
Purchase a GRE practice book to learn tools to help you get through tricky questions. Some recommended GRE books are by Kaplan, Barron and The Princeton Review. Some of them come with CDs and website memberships, so take advantage of everything they offer.
Use practice tests that you can find in the practice books and free online. This gets you familiar with the format and style of questions so you can be prepared. While you don't need to time yourself the first few times you take them, eventually you will want to time yourself so you get used to working with a time limit.