It's hard to give advice without more detail. How did you study up to this point? What are your specific areas of weakness (e.g., sentence correction)? Did you have lots of time left or run out of time on the practice exam?

Also, as far as a jump from 590 to 720 in two weeks, in all my years of GMAT teaching I think I've only had one or two students make such a vast improvement so quickly (so, it can happen, but it's not likely). If you're truly intent on getting that score up and are willing to take the necessary steps, you might want to push off your test date a little.

Thanks for the reply Jim

After reviewing my mistakes on the test, I noted the following

Quantitative
Of the 17 wrong question,
No. 30,31,32,33,35,36,37 were guesses as I ran out of time.
Of the remaining 9 wrong answers, 5 were silly interpretation mistakes, 4 I still can't solve.

Verbal
Of the 12 wrong answers,
No. 34,35,37,40,41 were quick guesses as I ran out of time.
The rest of the 2 SC, 2 CR, and 3 RC (from 1 passage) mistakes were really silly mistakes. In order of strengths, I'd say my SC & RC is better than my CR. With SC, I usually hit a 85-90-95% accuracy. With CR, maybe around 75-80-85%

I can't really pinpoint to any specific weakness. After solving all the questions from OG11, Kaplan and Kaplan 800, I noted that quantitative (except geometry) is a weakness for me. I know of most formulas and fundamental knowledge, I think I'm have problems in linking 'what I know' to 'how to solve the question'.

I've noticed that Gmat quantitative questions can be solved very easily... but the problem for me lies in figuring out how I can use fundamental maths knowledge to solve the question. It can take me a while to figure out the solution.

11 days left for the exam.

It sounds like we've pinpointed the problem: your exam pacing is off. Most of your mistakes were from guessing because you ran out of time - you just need to get faster. Do as many practice problems as you can now, because (of course) the better you are, the faster you'll be.

It is true that the earlier questions do count more, but you still don't want to be guessing on the last 7 questions.