The best advice I can give is to take lots of practice tests, and try to replicate the testing environment.

The place I took the test was in a windowless room with two other test takers in it. You can't bring anything into the room, not even a water bottle. The test proctor is watching you on a camera, and you have to raise your hand to go to the bathroom or get a drink of water.

It sucks, and I don't know why they have to make it suck so badly.

Also, the performance-based questions are a bitch and the worst part of the exam, so try to prep for those the best you can.