Be familiar with the requirements and regulations of the test. For example, go to the web site look up the registration process, deadlines, how to request interpreters and how to get extended time if desired. Be sure you know what this means. This will help you determine how much time is needed and how to structure your studies based on the time before you test. Take a practice test.
Many companies publish practice manuals.
These help you identify weak areas. If the test you are taking will be on computer, you may want a to get a CD of practice tests as well. Establish a group of people you will either study with or will report your progress to. This will help you keep on track for your studies. Some schools will not require you to take the GRE in certain situations requiring special accomodations.