Look at the answers for those tests (and explanations if available for the Manhattan), and try to see what types of questions you struggle the most with. Were you tricked by a falsely appealing answer or did you second guess yourself because something seemed too easy (I did that often on my practice tests)? Try to take those things into consideration when you take your next practice tests.
The other thing to consider is which section of the test is more important for the program you're going into. For a humanities/arts guy like me, verbal is more heavily weighted, but STEM people should do really well on the quantitative side to be competitive. Focus on the one that matters more, since you have a relatively limited amount of time left.
For an update to the above, I'm still waiting on my AW score, but my unofficial scores were in line with my practice tests:
Powerprep 1: 170V/160Q
Powerprep 2: 169V/157Q
GRE (unofficial): 169V/160Q
You still have more time to work on your skills than I did, though. I took those tests two days and one day before the test respectively.
If you can't retake the GRE to improve your score, the best advice I can give is to focus on your academic record. Have you taken and gotten a string of A grades in upper-level math courses? If so, that should help to combat the idea that your preparation is inadequate in some way.
Test is tomorrow, and so because I'm cramming (stupid, I know), I did the second PowerPrep test today, and got...
Powerprep 2: 169V/157Q
Powerprep 1: 170V/160Q
This time, I was blindsided by some of the harder math questions, and so got a lower score. I got the same number of questions correct on each verbal section as last time, but my score is one point less, for some reason.
Still optimistic, at any rate.
Taking the GRE on Thursday, took my first PowerPrep test today, and I got:
PowerPrep 1: 170V/160Q
I'd be satisfied with that, but hoping to brush up on a few more math concepts in the next few days.
Columbia, maybe Harvard and Northwestern. I would go for University of Chicago as well, but then I would have to write another research paper on music between now and December. I didn't do music in undergrad, so I don't have a backlog...