text: Sadly, despite what the publishers of tons of different products claim, it's hard to have a huge impact on your GMAT scores quickly, so don't go that route.  Assuming you have some time, the best way to increase your scores is to increase your vocabulary.  Read as much professional literature as you can get your hands on.  Remember, a little stress will help you, but a lot of stress will kill your scores.  Get up early the day of the exam and eat a good breakfast, wake up that brain, then as best as you can, 'relax'.  I've known lots of people who've tried a lot of different methods, but the key is to FEEL confident, FEEL relaxed and be CONFIDENT.  Your scores will improve.