This is a routine I learned from a powerlifter and within a month my abs were sticking way out (not gh style).
Sit on a steep incline bench, one that you can hook your feet into for doing situps. Lower yourself about halfway down, stopping at the point where you feel the most resistance, then hold for a slow count of 5, then go back up. That's one rep, aim for at least 5 sets of 5 in this manner. Once you can do that, either add reps or a little bit of weight. I went from my own bodyweight, to 5 sets of 8 reps with a 45lb plate, and now I can even see my abs through some of my t-shirts, and I only train them 1x per week. Not only does this build great abs, but strengthens your midsection so that you don't sway at the bottom of a squat.