I would have to say that the biggest difference between the first and second attempts was attitude. I was quite nervous before the first GMAT. I had a very hard time falling asleep the night before, and it was all I could think about in the days leading up to the test. The first problem I got in quant was somewhat tricky, and I panicked a bit and that killed me.
This time was totally different. I was perfectly calm, and everything seemed pretty easy. I was actually a little worried that the math section didn't seem more difficult, but it turned out fine in the end.
During the month between my first and second attempts I focused almost entirely on math. I went through about 12 GMAT club challenges, and these were fantastic. I had a number of very similar problems on the actual GMAT, and the challenges greatly improved my speed and accuracy on DS, my most problematic challenge. I highly recommend them to anyone who has trouble in quant. I also bought all 4 of the
manhattan GMAT math books. I was not impressed by the problems in the book, but the explanations of some concepts were helpful. What I found to be the most useful aspect by far of the
manhattan gmat series was the 6 CAT tests you get access to by buying their books. These were very challenging, and compared to most of their tests, the real GMAT was easier.
My verbal score did drop quite a bit, but not enough for me to care that much, although I was hoping to stay in the upper 40s. I think there were 2 reasons for the drop. 1. I focused almost entirely on math for the last month, with the exception of the CATs that I took. 2. When I was going through the verbal section, I felt I had done much better on the math than last time, and I was excited to get to the end of the test. I was also starting to get pretty hungry by midway through, and the combination of the two lowered my concentration levels.