In addition to the usual suggestions of getting a good night's sleep, and eating a good breakfast the day of the test, I suggest the following:
1. I have my students go to the test site prior to the test, especially in high-stakes situations such as the GRE. I recommend they do this from one to four weeks ahead of time. They check out the route and the parking situation, and mentally picture themselves going in and coming out of the test site door with a happy and confident disposition. If the student has not yet done this, that is still a good idea to do about 48 hours prior to the test.
2...