Hi MelP,
To start, improving from a 470 to a 580 is a significant achievement - so you clearly have the capacity to learn and improve. Raising a 580 to a much higher level will obviously require more work on your part - and it will be a bit tougher, so you have to be prepared to make the necessary changes to how you study and how you approach the Exam.
Before I can offer you the specific advice that you’re looking for, it would help if you could provide a bit more information on your goals:
1) What is your goal score?
2) When are you planning to retake the GMAT?
3) When are you planning to apply to Business School?
4) What Schools are you planning to apply to?
GMAT assassins aren't born, they're made,
Rich