It sounds like you are on a high level already, lucky you.
Not sure what kind of test you took but you should definitely download the free Gmat prep software on MBA which offers 2 official tests that give you the best idea of where you are right now.
The most important thing now is that you have to review all practice questions ( right and wrong answers ) so you understand the concepts of different question types. Ideally, you learn those concepts by heart so you can use them in the official test when you see a similar problem.
Other than that, GMAT requires practice. You can get to a point where you feel very comfortable with the whole format so invest as much time in your preparation as you can, it will pay off.
Know all the formulas and shortcuts to save time for difficult problems and you will have a chance to receive 720 if you are at 690 already.
Good luck!