tighten up you core with planks
It seems that, these days people are fixated on there abdominal muscles and when you ask someone what part of their body they want to reduce, it is almost invariably, the stomach, gut, spare tire or abs!
I use the term core because it encompasses, more than the stomach. The core muscles include your lower back and oblique muscles as well.
Planks, and the myriad of variations, are one of the best exercises to stabilize and strengthen your core muscles.
Start with improving core stability. Try hold in a plank in the position pictured here, or on your hands, palms flat on floor(push up position) Hold for as long as possible. If it was 5, 8 or 10 seconds, then do 3-5 sets of that number.
You should do these every other day, and try to increase the time of each rep each time.