Stay at or very near to the airfield the night before, even a short 30 minute drive will take away some of the precious mental capcity that you will require for this test.
Get as much stuff as possible ready the day before including notams, performance etc and makesure you get about 10 hours sleep!
If you have to fly a transit flight to the test centre, get the instructor who is with you to fly the plane as you need to be as fresh as possible for this test.
Good luck!