The GMAT test is a statistically-normed test (AKA "standardized") that students take before consideration for entrance to an MBA program. There are several steps involved in taking the test:
One of the things to remember about your GMAT test is that it is not the end of the world if you do not score in the 99th percentile. Even a score in the 50th or 70th percentile can be more than enough performance if your grades, work experience, and other admissions criteria are adequate.
When you take your GMAT test, it is best to be well-rested, eat a good breakfast, and show up to the GMAT test room a few minutes earlier. Even these little things can make a huge difference in your test performance.