First thing is: Do you need to get a high percentage of the questions on the test correct in order to get a high score? You have to know math formulas and grammar rules and other things, but these are just the things that look outside. It is more important how you take the test in a section.

On the GMAT, everyone takes a different test. The GMAT is a computer adaptive test, i.e. it actually changes based on how you are doing. It adapts to you while you are taking it. The test is not scored based on percentage or number correct answers.

Just getting more questions right doesn't increase your score. The GMAT scoring algorithm doesn't look at how many questions you answered correctly in a section. Instead, it looks at the difficulty level you've reached by the end of that section, i.e., it is a 'Where you end is what you get' test. You could reach the same difficulty level by missing a lot of questions, or by only missing a few, depending on where in the test you miss them, which questions you miss and whether you finish the section on time.

It is the case that if you answer approximately 60% of the questions correctly, you could end up at a 500 or 600 or 700 scores. The good scorer misses same number of questions throughout the section, i.e. misses roughly every other question. The low scorer regularly misses easy questions, whether that's because one is weak on the math basics, or because one makes careless errors. The good scorer misses hard questions and that too consciously and intentionally. If you are probably going to get a question wrong, you choose to get it wrong quickly and spend your resources elsewhere. The GMAT is explicitly trying to find the level at which you cannot answer questions correctly. And it will, even for someone scoring in the 99th percentile.

Another thing is: Are the earlier questions on the test particularly important? As you work through each section of the GMAT, the test will get harder or easier when you answer a question correctly and incorrectly respectively. These changes in difficulty level are more at the beginning of the section than at the end. This infers as if the earlier questions are more important than the later questions.

However, that isn't really the case. Getting the earlier questions right on the test would rapidly increase in difficulty, up to the maximum level. However, your score isn't based on the highest difficulty level you attain. Instead, it's based on the difficulty level at the end of the test. A solid start is nice, but spending extra time on the early problems means having very little time to answer hard problems later on. You might even run out of time at the end, which carries a heavy score penalty. So, if you can answer all of the early questions correctly and quickly, go for it. Otherwise, work at a steady pace throughout the test, and proactively guess on hard questions that you can't answer quickly, i.e. even at the beginning of each section.