The GRE is essentially divided into two parts that test your command of the English language and your command of mathematical skills and concepts in a multiple choice format. Most students generally have a better grasp of one subject more than the other but that doesn't have to be a stressful factor in your study progress. You will also have to write two qualitative essays, but they will be focused on your English skills.
First of all, you need to decide when to take the test, and the score reports can take 10-14 days to be sent to your school, so make sure you find out the application deadlines for the schools you are going to apply to and take the test, at the latest, a month before all applications are due. If you think you may want to retake the GRE a second time, if you don't get the score you want the first time, schedule the test at least three months before applications are due. (If you decide to take the hand-written test instead of the computer-based test, you have fewer dates to choose from, so book your test date early). A good tip is to schedule the test on a Monday, because it is the beginning of the week, your mind is usually at its peak and fresher than the rest of the week.
The next most important tip for the GRE is to take a practice test before you start studying. This way you can identify your weaknesses and focus on them during the study process, and save time from focusing on issues you don't have problems with.
Next comes the hard part, the preparation and study for the GRE. There are several books that have been published for GRE test-takers and some of them are better than others. The best reviewed and most helpful books are those published by Kaplan, Barron's and Princeton Review. They have GRE books that will prepare you and teach you all formats of the test.
However, if you think that you need more help in math, it is helpful to get a review guide that is specifically for math and go through the basics again. Many people haven't taken math in a long time and need to refresh and review the different math types and formulas. Some good guides to consider are Math Review For Standardized Tests (Cliffs Test Prep) and The Ultimate Math Refresher for the GRE, GMAT, and SAT.
It is also helpful to get books that focus just on vocabulary so that you can improve your word base with synonyms, root bases and meanings. This will prove extremely helpful in the verbal section, where the more words you are familiar with, the easier the test will be for you.
The best guides will tell you to set aside a couple of hours each day to study for the GRE and if you do that you are sure to score better than you would have with minimal study.