Seriously - just practice. Then practice some more. And practice more. No offense intended, but the time you spend on this forum could largely be better spent practicing questions. Don't overfocus on difficult questions like those in the math and verbal forums. Work your way up - when you can nail down 20 out of 20 easy questions, move on to medium. When you can get 20 out of 20 medium questions right, move on to hard. But you won't learn hard questions like Kaplan if you're still struggling with medium ones. Almost all of the "hard" GMAT questions I've seen so far can be broken down into easy parts. Time is your worst enemy - practice with time constraints a lot.