For your own protection in the matter, when once you've begun to study GMAT, here are a few of my favourite things to look out for.
1. Don't start late: a 10% score improvement can takes 5 hours of coaching and perhaps 2 weeks to sink in. This is a test of skill, and training cannot be crammed. Many students start to study in the last 2-3 weeks, and they needlessly cap their scores far below potential. Give yourself a margin for error, and plan 2-3 months ahead.
2. Don't Burn Questions: Real GMAT questions are profoundly interesting, ad ntake months to write, edit, test, and polish. There is Phd staff of Mathematicians, Logicians, and Statisticians, dedicated to creating a pool of airtight questions, without errors or ambiguities or idiosyncratic phrases. They run these questions against hundreds of thousands of test-takers, to iron out the wrinkles in a way 3rd party materials just cannot afford. That makes such questions still very rare. 3rd party materials, though many have value, still cannot significantly replace the GMAC-made materials. That is why it is not wise to use those official questions naively, for example to practice basic ideas of grammar and math. Resist the temptation to engage with the professional materials until you understand exactly what is to be done with them. There are several considerations, but the main one is Beware, these questions are not like candy. Talk it over with an expert, and accept guidance, so that you do not end up having used all the good stuff, still need to practice, but nowhere else to go.
3. Hire Many Experts: So many students start out by taking a GMAT course, or by signing up for a package of private lessons. These are big decisions, involving a commitment of much money and even more precious time. In Amsterdam, there are, by luck, several inexpensive GMAT courses, but that doesn't mean you won't waste time and money on the wrong program. Read our ideas about how to select a good online course, ideas that apply to in-person courses also. Even more importantly, try to set yourself up with multiple inputs. Don't tie yourself down to just one channel. It will take several weeks before you realise the real value of what you bought. In the best case, you find a real guru of GMAT. Or maybe he is a guru, but not your guru. Why have only one guru? Is your guru such a baby that he can't handle it when you learn from someone else? We are sure that we offer by far the best in-person course of GMAT in the Netherlands: nobody else beats us on hours, money, or value-for-money. But there are also several great resources online, and some are even free. Khan Academy, for example, goes over each math question in the Official Guide, and that would be a very valuable companion in the middle stages of study.