I just took the GMAT test last week and got the result of 610 (Q:39, V:34) and AWA 6.0... I spent six weeks for preparation and did all the MGMAT books and the 12th edition of OG and the 2nd edition of both verbal and quantitative OG books. Prior to my test, I took several practice tests from GMAC, Princeton, and MGMAT. Here are the results of them.

1. Official GMAT Prep 1: 540
2. Official GMAT Prep 2: 580
3. Princeton 1 (Q40, V30): 580
4. Princeton 2 (Q35, V38): 600
5. MGMAT 1 (Q37, V35): 600
6. MGMAT 2 (Q44, V37): 670
7. MGMAT 3 (Q44, V33): 640

I was hoping for the score around 650 but all I got was 610 and am pretty disappointed...
My weaknesses have been both sections of math and critical reasoning.
I need some advice to improve my overall score and I'm looking for the score around upper 600 eventually... I have some time before the next test because I haven't registered for it yet.
While I was taking the test, I was a few minutes behind the time, which had never happened before... I think the concentration was wearing out towards the end of the test too.
If anyone could tell me what I should do to improve my score, I would seriously appreciate it.

Thank you.