GMAT Strategy

I ended up scoring 630 (V28, Q48) today on my GMAT Test. Not sure what happened to my verbal test in fact. Right after I have finished the verbal, I thought I have done a good job to get at least a 34, which is the average I have been getting when I did my practice test. Further, I actually saw a difficult SC question in the middle of the test, those with the whole sentence underlined (which made me say "YES!!" silently during the exam ). Hence, I can probably conclude that I did pretty badly towards the end of the test, which I did not realize, as I have finished the verbal exam on time.

I think I did a pretty good job in the rest of the exam though. As I am not retaking my next one until 11/19, I have more than enough time to improve my score. Any advice on how I can improve my Verbal score? I am thinking about doing a few more Manhattan and Kaplan practice tests. Should I also redo the two GMATPrep Tests? I have finished the Orange and the Purple books. Lastly, should I invest any more time on Math?

Here are my results of my previous practice exams -

Test Name Date Taken Verbal Math Total
Princeton Review #1 9/9/2008 28 42 580
Princeton Review #2 9/22/2008 30 50 650
Princeton Review #3 9/25/2008 34 44 640
Princeton Review #4 10/4/2008 37 43 650
GMAT Prep Test #1 10/12/2008 33 47 670
GMAT Prep Test #2 10/13/2008 31 48 640
Manhattan Review 10/14/2008 34 47 670