Here's a great read:
"22. Doing a million crunches. The secret to six-pack abs probably isn’t crunch after crunch. To flatten out and tone up the core, try running some intervals, lifting a few weights, and cleaning up that diet instead."
Healthy Habits That Aren't So Healthy
Working at a gym, you don't know how many times you hear people say they want to lose their stomach and get abs. Then they proceed to do a hundred crunches. That is the worst thing you can do--you won't lose belly fat (you can't spot reduce) and you might end up hurting your lower back.
The best recipe for six-pack abs is to stay on top of your nutrition. Things have to be near perfect to have that hard chiseled look. And although I have 19% body fat overall, I don't even have six-pack abs because I enjoy the occasional drink and some chocolate.
Discipline is key. First is nutrition, second is strength training, third is cardio. That's my recommendation for losing body fat and working toward a flat stomach!