Pack reinforcements. Besides the standard items like your admission ticket, a photo ID, and pencils or pens for scratch work, you'll want to bring a small snack and extra clothes with you. Dress in layers, as test centers are notoriously either too hot or too cold. Don't bring scratch paper, calculators, or digital watches, none of which are allowed. (Watches with hands are fine.) Your proctor will provide scratch paper, and there's a clock on your computer screen.

Pace yourself. Because the first five questions of each section are so important, start slowly (although there are limits to this if you are aiming for a very high score), and then speed up. The onscreen clock automatically stays on during the last five minutes of a section, but it can be turned on and off during the rest of the test. Turn it off during the first five minutes so that you don't feel pressure while answering these crucial questions. Guess strategically. Guess only if you are really stumped or tight on time: If you have 6 to 10 questions with less than five minutes left, try to eliminate at least one wrong answer before guessing. If you have 11 or more questions to go with less than five minutes left, guess randomly until you get to the last question, and spend all of your remaining time on that one.

Take a break. The CAT includes two optional five-minute breaks. Take them. Don't outsmart yourself. Don't get too caught up in your knowledge of how the test is scored and overanalyze the difficulty level of every question. If you get what seems like an easy question, don't panic: It might be a trick problem, an experimental question, or just one that's simple for you but hard for others. "Always concentrate on the question at hand," says one GMAT tutor. "Don't worry about the one before it or the one after it."

Don't rush to retake the test. Of course, it's always possible that you will get really flustered or have some other experience that causes you to score poorly on the test. But think twice before taking the GMAT again. Do you have a legitimate reason to think your score would improve a second time around? Was your score low because you weren't familiar with the test format and types of questions? Do you have one or two clearly identifiable weaknesses that targeted study could improve? If so, you may be a good candidate to retake the test. The same holds true if there were extenuating circumstances -- a personal trauma, illness, uncontrollable nerves, or a poor night's sleep.
However, if you absolutely killed yourself studying the first time, you may be too burned out to do it all over again. Score jumps of 100 or more are unusual, and your score won't just magically go up because you've taken the test before. If you've taken the GMAT twice or more already, you've probably done all the improving you're going to do.