There is no such thing as a "spot reduction" for fat loss. Though we all wish it were possible, you can not simply lose fat in any one specific area of the body.
Diet is 80% of the battle when it comes to fat loss, especially in the abdominal area. The first thing I would recommend, and I know this sounds a bit scary, but try to eat MORE OFTEN. Eating more often helps speed up your metabolism because when you are only eating a couple times a day, your body is tricked into "survival mode." When you don't receive nourishment on a regular basis, your body is actually tricked into holding on to extra fat because it is unsure of when it will receive nourishment again. It's sort of a reverse way of thinking, I know, but that's what happens. Aim for 6 small meals a day, consisting of 1 complex carbohydrate, 1 lean protein, and unlimited vegetables (green leafy vegetables are the best choice.) Also try to get 2 or 3 servings of healthy fats in your diet. I like natural peanut butter in the morning, and maybe a handful of raw almonds or cashews later in the evening. Avocados are also a great healthy fat.
Another tip is to drink about a gallon of water a day. The same sort of survival mode I described withbody fat also pertains to water weight. Believe it or not, your body could be holding an extra 10-15lbs of water weight! You can flush your system by drinking lots and lots of water each day, and retraining your body to let go of the extra water it's holding.
After you've adjusted your diet, you should start seeing results very quickly, I would say 2-4 weeks.
To maximize results, try adding weight training 3-4 days a week. Muscle burns fat, so the more muscle you have, the more fat you will burn at rest.
Hope this helps :)