My only tip is to practice, practice, practice because you CAN train yourself for this test. Be honest about your weaknesses, and work on those the most. In your case, if vocab and reading are the issue, buy yourself a prep book and or find tests online. I used The Princeton Review: GRE | GRE Test Preparation
. For vocab, I literally wrote down every word I came across in the practice tests that I didn't know and just memorized as many as I could and it actually worked for me.
Sorry if this was terribly obvious! Good luck!