GMAT Strategy

Hi All

I have my GMAT scheduled in exactly one month from now. I have been using the MGMAT study guides and have completed practicing the Official Guides twice. I gave 3 practice tests last month with scores as follows:

Practice test 1 Kaplan 2012 : 620
Practice test 2 by GMAT Prep : 660
Practice test 3 by Manhattan online : 600

These are not the best of scores I am expecting. Can anyone suggest on how to go about the preparation from now? I have 3 practice tests from Kaplan and one test from GMAT Prep remaining. I can easily spare 4-6 hours per day for the studies.

Thanks

Richa