Okay, I've only got 13 hours but....
Death grip on the contol column. Hold the controls lightly, the a/c isn't going to suddenly dive for the ground
Get your seat in the right place, count the number of visible holes in the seat runner so you get it the same every time
Try not to worry about landing. My landings are somewhere in between certain death and contolled crash at the moment but I am assured that it will come eventually
Don't be afraid to ask your instructor if you don't understand something. Keep asking until you do understand, they're there to help you
Don't worry, you'll really enjoy it
Er, that's it for now, I'm going home for a beer