Planking is a great example of an abdominal exercise. Not only will it help you get a flatter stomach, but it will also build your core muscles and make them stronger. To begin, get into a push-up position and only hold your body up by your elbows and toes. Keep your body as straight as possible. Now, tighten your abs and hold this position for at least thirty seconds. If your schedule permits it, try to do planks three to four times per day.