Make sure you study a range of problems. Many of the practice problems in books will sound fairly easy, but if you're doing well they get harder in the next block of questions (unlike the old GRE where they got harder each question you completed). I was thrown when I realized it had gotten a lot more complex, and the books don't really tell you this will happen and they don't provide you with more challenging questions. Do a lot of practice, over and over again, on a range of problems in algebra, geometry, etc. Especially when you are a little rusty on math after being out of school for a year or two, or haven't used anything but stats problems and software... it might take a little longer to familiarize yourself with the subject matter. Even though it's "simple" stuff, they try to make it harder. I used Barrons and Kaplan, and they were good for the easier problems, but again..based on what I wrote above, it doesn't prepare you for the more complex ones.
Also, make sure you work on your timing. I remember for both sections I wasn't even able to make it through, and had several questions left over at the end that I hadn't gotten to simply because I didn't realize it would be as challenging as it turned out to be.
This was true for both Q and writing for me - I did well on the writing, not so hot on Q, and again... not so hot on V either, but I didn't get to complete my essays! Also, make sure you give yourself enough time to receive your scores, evaluate and retake the test if necessary. If I could go back this time around before applying to grad schools, I would have given myself at least 5 months between the first GRE and applications, instead I only gave myself 2.
Additionally, I didn't study all that much because of a last minute publishing opportunity that arose, but if you want to do well and aren't sure you will, give yourself the time to study and the time to retake them if necessary. If you do that, you are bound to hit at least your lower mark in accomplishing whatever scores you need for the programs to which you want to apply.
Good luck!