Have you taken the Powerscore or Official GMAT Practice Tests yet? What was your break-out (Quant & Verbal)?
I liked MGMAT (Manhattan GMAT
) because it provides you with your own error guide and shows you what types of questions you got wrong, what you got right, how long it took, etc.
I don't believe the math in MGMAT is at all realistic but if you can do well on those tests, you should do fine on the real thing.
Take some practice tests, do some analysis and find your weak points. Once you have that figured out, you'll be able to raise your score.
Another good place to start is the Chinese Zip files (PS, DS, SC, CR, RC).