1)Don't forget to urinate! Make sure you empty all of it out prior to sitting down in front of the computer. More importantly, don't drink sweet stuffs because they tend to make you go pee faster (remember those stuffs about maintaining a normal glucose level? hehe)
2) Dress comfortably and nicely. It will help boosting your self-esteem which could lead to better performance. Remember, it's all about looking good!
3) During your break time, spend just a few minutes using the restroom. Go back to the testing center as quickly as possible to refocus on the subjects coming up (i.e., reading and maths). You will also want to write down some difficult mathematical formula to better prepare for the math section. For example, you may want to draw some angles to save some time in case trigonometrical problems arise.
4) Check for incomplete questions when you completed the sections. Sometimes, if you are clicking too fast, you might miss out a question or two. It will cause quite a damage. Good luck buddy. Now go smoke that DAT!