There are a few things I would suggest; the biggest one would be not spending 10 hours a day on prep the week before the test, because you'll burn yourself out. I've always told students that they should limit themselves to 4-6 hours at the very most, and break that up into 2 hour blocks, because after that your retention suffers. 4 good hours of studying with your attention and retention at their peaks will yield better results than 10 continuous hours of slogging through the material. During your study breaks, do things that will put you in better mental and physical condition for the exam: take a walk outside, nap for an hour or so, watch a funny movie, or spend time enjoying the company of friends and family. Nurturing a positive outlook and an overall sense of wellness is crucial to success on this exam, because it is designed to test not only your quant and verbal skills, but also how well you handle pressure, which has a direct relationship to how well you'll handle the rigors of business school.

Other than that, there are some more obvious things: make sure to address all of the wrong answers and why they're wrong, as well as the right answers and your chosen answers. Read things that are written correctly, because that will help you develop an eye for correct usage. A good choice is the book The Elements of Style, which discusses the kinds of rules that you'll need to know for the SC section, and has the added advantage of being well-written itself. And finally, if you haven't already done so, it might be worth investing in a few hours of private tutoring. I think it's fairly common for students to get that kind of last-minute help, and it can often be valuable because a tutor can diagnose recurring problems in the way that you approach sentences.

Hope this helps, and good luck!