Check out this site for tips http://www.ab-core-and-stomach-exercises.com
References :

You should eat cleaner. Simply, lose the junk food. Since your body seems to store most of its fat in your belly, in order to burn this off, you must eat fewer calories than your body burns daily- don’t starve yourself though. Keep a log of what you eat for 3 days and count your calories (use http://www.fitday.com). Then, once you’ve figured out how much calories you’ve been taking in, reduce by about 200 calories. With the reduction in calories, do the following:

Cardio, 3 times a week. Cardio will reduce your body fat. In your case, since your body stores most of its fat in your belly, you should notice that you will be burning the fat off, then losing some weight because of it.

Now make sure that you incorporate some weights into your regimen in order to maintain or even gain some muscle. Too much cardio may destroy some of your muscle- don’t go by what the scale says in terms of weight, measure your bodyfat using bodyfat calipers.
References :
http://www.bodybuilding.com