Jumping Oblique Twist – This is a great cardio move to help burn calories, minimize belly fat and tone the sides. Oblique moves like this one create muscles that pull your body inwards, creating the look that you're after.
The Russian Twist - The twisting motion of this exercise whittles your middle by firming the muscles on your sides; giving you a toned, smaller midsection. The jumping around also bumps up your caloric burn, which is important for maintaining a healthy bodyweight.
Pilates Side Plank with Leg Raise – This is a challenging, effective exercise for the entire core; you will immediately feel your sides and obliques working. There are multiple levels of difficulty for this move; choose the one that you can do with perfect form.
Crisscross Crunches – One of the best ways to tone your stomach and see results fast. This is an exercise that burns a good deal of calories, due to all of the large muscles groups involved; your whole body has to chip in to create this motion.
Windshield Wipers – A good beginner obliques exercise that improves range of motion around the torso. You can make this one harder by straightening your legs, but only attempt that modification if you already have a solid foundation of core strength.