I'm not an expert on the GRE (LSAT and MCAT are my specialties), but I know a little bit. The test is changing radically this fall--or so ETS says. They've already put off rolling out the new GRE general test once, although I'd be surprised if they put it off again.
As long as you're taking it before September, the test format is the same old tried-and-true GRE (read: the old-old SAT with 2 essays, harder vocabulary, and easier math).
If you're looking to come to our program, GRE math shouldn't be a problem for you. ETS's official mock-test is free to download, gets you used to the interface, and gives a reasonable sense of what you can expect. To prepare for the verbal, I'd recommend starting with a one-stop-shopping guide such as Princeton Review's Cracking the GRE. The math won't be particularly useful to you, but believe it or not there are verbal techniques that can improve your score; it isn't just memorizing vocabulary.
Of course, memorizing vocabulary doesn't hurt. If the resources in Cracking aren't extensive enough for you (I haven't seen the book in a few years, but if memory serves, those lists are a little light...), then I'm sure you can find something in B&N that just drills GRE vocabulary. In the end, this is the major thing the GRE verbal tests, which is silly but then the whole idea of this test is rather silly, in my opinion.
The essay is a bit tougher. If you have resources such as a college writing center or a very helpful friend with an English degree, you might try writing some practice essays and ask for opinions about how to improve them. Cracking has some good big-picture advice about writing for standardized tests (one of my favorite exercises but, ultimately, even sillier than the verbal section), but in order to improve your score you really need a human to look at what you're turning out.