There are 2 parts to having good abs. First you need the muscle there, so that means core exercises like sit-ups, crunches, planks and medicine ball work.

Second, you need to remove the fat. The more muscle you have the more fat it will burn but you'll want to look closely at your diet and how many calories you taking in versus what you are burning. You need to burn more than you take in to lose fat.

One last thing, doing ab exercises doing ab exercises doesn't burn fat from your abs. All working out burns fat from everywhere.