No matter how many ab workouts you do, they won't help you reduce belly fat. Instead of focusing on spot reduction — targeting one specific area on your body — you've got to train your entire body, fuel up with nutritious foods, and make sure that you're recovering (nope, all-nighters won't help) to lose fat in general. And losing body fat all over means you will be losing some on your belly as well.
Here's something else most people probably don't know: Fidgeting is good for you. It's considered a nonexercise physical activity, and it's an important way to burn energy. You get more health benefits if, in addition to exercising, you are a more fidgety, more active person the rest of the day. This means gesturing while you're talking, tapping your foot, just moving around.