Before even really studying, I was scoring 340-350. I purchased Kaplan's "GMAT Math workbook 5th.ed" and worked through the many practice questions and examples, and scored significantly higher. Whether or not it was because of the book, or just practice remains in the air. However, I do feel much more comfortable setting up questions in a more efficient manner.
I purchased this book because many of the people on this forum recommended a GRE/GMAT math workbooks..for 17 dollars it was worth it IMO.