I am not where you are yet, but here's what's been suggested to me:
In the last few days, maybe take one test, but do that several days before, not the day before. A fluky test score just before your test can freak you out. Don't suddenly try a different company's tests the last week, either. If you've been doing PR the past few tests, do a PR one last. Or do a GMATPrep last, no matter what you've been studying. Those are most like the real thing, and I hear that lots of people save one of those for their last. If you've already done both GMATPreps, then stick with whatever you're doing as long as those tests are working for you.
Otherwise, I'd do a few practice questions each day from each section, whether they're weak or strong areas. Do a few extras in weak areas, as long as you're not still trying to figure it out altogether. Review your fundamentals, and if you've made flashcards for math formulas, grammar rules, etc., review those casually. No cramming!
The night before, watch something silly on TV or hang with friends. Don't party or hang too late, though.
Now after you've taken it, let me know if this advice worked. LOL. I've only read about it, not done it yet!!!
