I don't have a lot of advice on the actual contents of the GRE, as this site isn't really geared toward that. But here's the advice I do have:
- STUDY. Seriously. I don't care how great you think you are at math and vocab, or how well you did on your SATs. Study for this one. It's different. It's harder. Let me tell you a story. Once upon a time, there was a girl (with red hair, and glasses) who didn't study for her GRE. Her resulting score was not even high enough to apply for graduate schools. The next time, she studied for, oh, only about two months or so. Her score went up almost 350 points, and is now considered extremely good. It pays to study. Trust me!
- Make sure you are taking it on a good day. By a good day, I mean you are in a good mood, relaxed, nothing majorly bad is going on in your life, and for god's sake, you are not hungover, drunk, or on drugs. If any of these things applies, cancel. Cancel your GRE and take it next month. I mean, you can take it, sure. But schools are going to see all your scores for the past five years.
- Try this website. They have a free GRE prep. It's pretty much all I used to study the second time I took the GRE, and I think I mentioned the noticeable score difference.
- Take the GRE with plenty of time to take it over if need be, and at the very least, plenty of time to get your scores sent to your schools on time. I'd say September or October would be the absolute latest times to be taking your GRE.
- Keep in mind that the subject test is not offered constantly like the general test. It's only offered two days a year (usually April and November/December). Even if you don't need to take it, it can't hurt, so make sure you take it the winter or spring before you apply - don't wait until the winter you're applying, because it'll be too late.