Hi asthagupta,
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 how you've been studying and your goals:
1) How long have you studied?
2) Did you take the ENTIRE CAT each time (including the Essay and IR sections)?
3) Have you taken any of the GMAC CATs (and if so, then how did you score on those)?
4) When are you planning to apply to Business School?
Given your last practice CAT score, and your score goal, you're going to need to improve in BOTH the Quant and Verbal sections. Thankfully, the GMAT is a consistent, predictable Exam, so you CAN train to score at a higher level.
GMAT assassins aren't born, they're made,
Rich