Take the practice tests (tons online) to get comfortable with it and to help catch your weak points but the simple reality is that it tests for stuff you can't really cram on. I went in and smashed the thing with a major headache and very little study since I'd already been unofficially but definitely accepted to grad school and for a long while I wondered how much higher I'd have scored if I'd studied more and gone in sans migraine. Eventually I realized the answer was "Probably only a little higher" because at most it would have bought me a bit more time to review questions I was botching and staring at and rarely did I produce an answer to one of those even with the extra time. My basic knowledge was totally intact and built on years of study, not weeks of cramming, and my test taking habits had long since mutated from my youthful haste to the method of slow, steady checking and rechecking and coming back and checking again until the test time ran out.

I'm not saying not to study, to the contrary I'd suggest taking practice tests and reviewing the stuff you messed up on until you're comfortable or even bored of the material, but that just brushes off the rust and relaxes you about taking the test. But you can't cram for comprehensive multi-field subjects trying to measure your entire academic progress.