This exercise will get your buttocks in shape faster than anything else. Meet with a personal trainer if you can for more exercises to work this area at your local gym. Ab crunches to me are the best and safest way to work this area. There are a number of ways to learn new exercises. Most aerobics classes or group x classes work abdominal muscles for at least five minutes at the end of each class.
Some gyms offer abdominal classes only.
There is an ab crunch machine by Cybex and other manufacturers that work this area very well. Another challenging exercise for abs is standing leg raises. This is a more advanced exercise to work the abs. At home you can do some ab crunches yourself by laying down, knees bent, head back, finger tips behind your head, elbows open and look up at the ceiling. Begin by raising your shoulders only and lowering them using your ab muscles.