Taking the September LSAT?

Put away everything else and just study for the LSAT. You don't want to have to retake this test in December if you don't have to because there is a huge advantage to completing your applications as early as possible. You have 6 weeks. Now is the time to put away thoughts about your personal statement and schools and everything - preparing properly for the LSAT is the best thing you can do for your law school applications right now. Then, while waiting for your score you can do the personal statement, resume, addenda, etc.
Stay motivated! Don't think about a back-up test in December. Put everything you can into the next six weeks. And for those of you getting frustrated with your practice test scores, remember you still have 6 more weeks to improve. It's not too late to call a tutor and put more time in.
What is my #1 tip for LSAT prep?
Review every answer, even if you got it right. After all, you might've gotten it right by accident!
Good luck and hunker down!