Hi bthomas,
To start, a 580 isn't a terrible (the average overall score on the Official GMAT hovers around 540-550 most years). Depending on the Schools that you plan to apply to though, a retest is probably warranted.
Before I can offer the pointed advice that you're looking for, I need to know more about your studies so far and your timeline/goals:
1) What is your goal score?
2) How long have you been studying?
3) What materials have you been using?
4) When are you planning to retake the GMAT?
5) How were you scoring on your practice CATs (including the Quant and Verbal Scaled Scores)?
6) When are you planning to apply to Business School?
7) Do you know which Schools you plan to apply to?
Thankfully, the GMAT is a predictable, standardized Test, so you CAN train to score at a higher level.
GMAT assassins aren't born, they're made,
Rich