According to ETS you can't. This test is a pure measure of your ability to respond to certain math, logic and written problems.

Well maybe that isn't quite the case. Given the existence of numerous test preparation books and centers from the likes of Kaplans, Princeton Review, and Arco to name but a few it would seem that many people feel you can prepare for the GMAT. Even ETS itself publishes a book full of old questions so that you can practice before you take the real test. You can improve your score quite considerably by putting a little (or a lot of) work into preparing for the test. With effort you should be able to improve your score some 100-200 points, which will make a marked difference in the options you have for choosing a business school.

There are two elements to preparation. Firstly study. The mathematics (arithmetic, geometry, algebra, probability, sets etc.) is of a high school level but for exactly this reason many of you will not have seen these subjects in years and inevitably you will be a little rusty. Apart from a revision of the math there are numerous time savers and short cuts to be learnt. In the verbal section Sentence Correction is full of traps to catch out even the most confident native speaker of English so you will need to brush up on your grammar. In both Critical Reasoning and Reading Comprehension there are guidelines to follow which will improve your results and save you time in the test. Secondly practice. There is no substitute for practice in your preparation for the GMAT. The GMAT has strict time limits and without practice you will find it very hard to finish the test on time. Also, GMAT questions are all very similar and if you have already tried 200+ questions you will find that many of the questions in the real test are familiar and thus easy.