You need to build up both the gluts and the muscles that support them-- the hamstrings. Do strengthening exercises like squats, and lunges, but also do cardio to burn off the fat. I do a "butt butterfly" exercise-- you get down on all fours, and lift your leg to the side and out-- it hurts at first, but keep it up.
If you belong to a gym, ask any instructor-- they'll usually give you some good tips.
at 7:00 PM on Jul. 7, 2009