Interval training, also known as tabata sprints, is an incredibly powerful way to shed belly fat and get abs. Unfortunately however, most people don't know how to harness it's power and opt instead to run on the treadmill or cycle on the stationary bike for 20 minutes at a time, often at the same pace. There's nothing really 'wrong' with this per say as it does deliver benefits, it's just an ineffective way to train.
The crazy thing is that's it's an incredibly easy training style to use. While it does require more effort for short periods, you get plenty of time to gather your breath and rest before ratcheting up the intensity again, so don't worry! A great way to start is to set yourself 5 cycles of 10 seconds 'high intensity', followed by 20 seconds of 'low intensity' recovery. Typically, you would apply this to your cardiovascular routine, but the same principles can be applied to resistance exercises.
An important point to remember is to NOT stop moving during your recovery period. If you're working out on a treadmill, a slow walk is perfect and will keep you breathing and enable you to rest sufficiently before picking up the pace again. Interval training works as you're repeatedly able to fully exert yourself for short, manageable periods which is what separates it from more 'traditional' cardio routines.
The best thing about this training method is that you can modify and customize it to fit your needs and goals. As your level of fitness improves you can increase the challenge by reducing your recovery time or increasing your 'work' time. Here's an awesome video to get you started.