Reduce calorie intake by 500-600 cals/day under maintenance. Drink lots of water. Eat 1.3g of clean, lean protein per pound of bodyweight. Keep your complex carbs consumption to before 2-3pm. For ab work, do weighted ab excercises with a rep scheme of 5-6reps then immediately do another body weight excercise for 12-15 reps. Repeat that for 4 sets. Always change up your ab routine to keep the muscles building without hitting the "plateau" or "adaptation" stage. Since abs are a dense muscle, you can work them more often in a week, such as mon/wed/fri, remembering to change up your exercises. Try that.
P.S. the best ab workout I've found out is cardio. (Well the best way to see your abs)