I do 700 sit ups every other day and work with weights with my obliques. Many people tell me 700 is too much and I can get results by working with weights. The main key for good abs, which I found out first hand recently, is to maintain somewhat less body fat. I had to lose 15 pounds over the summer with extreme/intense cardio and after losing the weight, I got the abs I wanted. I always had the muscles, but it was hiding under that belly fat. The hardest part is lacking of the fat to keep the abs visible.