Hi. Not a whole lot really. You can't bring a lot of the things with you such as notes and they will ask you to put your phone into a locker and not touch it (it is serious and silly at the same time - so don't open your phone when you are done with the test but just walk out and then do it - stupid but still).
I suggest bringing a snack or a drink for the break (just in case), if you are planning to take a break and walk to the lockers.
Also, i highly recommend warming up before the exam and taking 5 or so questions to get your mind going and take it out of the stress panic mode. But you will have to do this outside before you go in/check in due to devices policy.
Have you taken the test already or this is the first time?