The fact that it is all about good preparation, and pattern recognition! Your GMAT score is directly proportional to how well prepared you are, and by that I mean how well you can recognize patterns. It is all about recognizing the patterns of questions they ask, and the answers they expect(even if in some cases you may not agree with them).
With sufficient and smart practice, one can get a good handle over the patterns and score well.
For example, SC questions are all about which rules they look for. The same holds true for CR - what are the traps, what are the fallacies, what kind of logical connections can you make.
You can gain a good understanding of these "patterns" by practising, and more importantly evaluating each an every question you practised, especially from the OG, verbal review and quant review. Analyzing the answer to each question in those 3 books(and GMAT prep of course), and the explanation for why the wrong answers are eliminated, are of paramount importance. Ideally, get done with the other practice material in the initial periods of preparation, to get familiarized with the concepts, and focus on these 3 books in the second half of your prep time. That way, you have a solid understanding of the fundamentals, and are ready to take on the real deal.
Keeping a log with key concepts, and mistakes you repeat on tests also helps a lot in improving the score.
For the record, I scored a 770.