For the best results you should incorporate cardiovascular exercise with weight training and abdominal work. Exercising aerobically burns fat and calories, and decreases the amount of fat that lies over the abdominal muscles. Many times people do hundreds of sit-ups and never see a change in their bellies – that’s because unless you reduce the fat that covers the muscles, you can’t see the definition underneath. Excellent choices for aerobic workouts are swimming, interval training, and speed walking. You should ideally work out four to five times during the week. Strength training is also important because you need strong muscles in order to power your aerobic training. Additionally muscle burns more calories than fat and takes up less space, too. The final part of your program is the abdominal work itself. Traditional sit-ups are fine but try moves with a twist for an extra boost in metabolism. Pilate’s moves are great for tightening abdominal muscles as is belly dancing. There are a variety of moves and routines you can incorporate into your schedule to move you closer to your ultimate goal of six-pack abs.
Detailed article on building abs: http://www.newagey.com/physical-fitness/six-pack-abs-without-supplements/