d-dub said:You need:
1) muscle mass - use progressive overload as you would with any exercise. If you can do 100 situps grab a dumbell and do them weighted.
2) Low bodyfat percentage - if your body fat percentage is too high you will never see the muscles you have developed. Diet is critical in obtaining a visible six pack.
As has been said many times "A six pack is made in the kitchen, not in the gym"
Hmm, or something like that...
Have fun
That pretty much covers it.
Don't laugh - but if you're new to ab exercises go out and get 'power sculpting abs' dvd/vhs from Winsor Pilates - about 20 min with resistance bands.