Lots of great suggestions. The Structural Engineering Reference Manual has a good checklist of items to bring or do (some are very silly, but most are very practical) .
Make sure you balance your sleep schedule the nights before. Get your sleep schedule setup for the time you need to get up for the exam. Don't go to sleep too early or too late and set two alarms (in the event one fails to go off). You will probably wake up about 30 minutes prior to whatever alarm you set anyway. Or, if you're like me and went to bed too early you'll wake up a few hours prior to when your alarm is...
Don't skip coffee or breakfast if that's your normal routine. Don't get coffee if that's not your normal routine.
Leave your phone, fitbit, google glass, copier/fax/scanner, etc. in the car! Don't get ejected for having some electronic device you're not supposed to in the exam room.
After the exam (and during lunch), TAKE NOTES! Write down anything you can think of. DO NOT SHARE THESE NOTES! However, if you unfortunately need to retake the exam these notes will be invaluable.
Optional: Arrange for a driver so that you can drink after the exam. Congratulations on getting your life back!
Good luck everyone!