Nutrition is key. You need your body fat % in the single digits which can be achieved by proper diet and cardio. you also need to bulk your abs up which will be achieved by a proper diet and weight training.
train your abs just like you would train any other muscle in your body. i do 4 sets of decline crunchs for 8 reps and also throw in 1 set of leg raises for 8 reps two times a week. all these are done weighted by holding a plate behind my head or for the leg raises i use leg weights.
ive done the billion crunches everyday program and didnt see anywhere near the results that i am getting now.
go check out
www.bodybuilding.com and read the forum for yourself.