What should I do the weekend before the GMAT?

Sorry I didn't see this before your test - hope it went well!

But for others... don't do much in the couple of days before your test. Do high-level review. Review your major strategies for the different question types, your timing plans, your educated guessing strategies, and think about what you will do if you find yourself, say, 5 minutes behind on time. How will you handle that? Think about what you want to write down on your scrap paper during the tutorial and during any extra time you may have during the essays.

Do a few problems to keep your brain sharp, but not more than about half an hour's worth.

Also, drive by the testing facility to make sure you know how to get there. Go to the grocery store and buy whatever you want to bring with you to the test center, along with whatever you want to eat for the meal before your test and for dinner the night before. Make sure you have the proper ID. Etc.

Go for a hike or do something else somewhat physical two days before - not enough to make you sore, but enough to ensure that you sleep well that night. Do something physical the day before, too, but not as physical / tiring as whatever you do two days before.