Just keep your cool when you go to the exam centre. You will see a few guys and gals as if the whole world has come down on their shoulders. Dont do that. It spoils your mood and preparation to a great extent. Just make sure you dont drink a lot of water(you know why). They wont allow you to come out untill you have finished essay+analytical. And remember, the first 12-13 questions and the last five questions are really important(this is the information for people who are trying to explore GRE for the first time).Give maximum time to these(but dont take a longer time on any one question). If you miss out some questions then prepare another $160 credit. Leaving questions will screw up your score badly.