The vocabulary was definitely the worst part of it for me! One of the words that turned up on the analogies had nine syllables! I'm sure, if I had wanted to, I could have figured out the root and then the myriad prefixes and suffixes that were tacked on, but I decided to skip that one
Meanwhile, the math was pretty much a joke. I hadn't taken a math class since high school, and I scored very well (pretty much without studying) on that section.
If you look on ETS's (the company that writes the exam) website, they should have a list of all of the possible essay questions, as well (or, at least they used to - I took the test five years ago, so it's possible that things have changed a little). I don't suggest you try and outline answers to all of them, as there are about 200. But it will certainly give you a sense of what to expect. It was super easy, IMO.
Also, don't know if this is still true, but it used to be that when you signed up for the exam, ETS sent you a CD with a bunch of practice tests on it - the sooner you sign up, the faster you got your hands on that disk.
Good luck, everyone!