Summarize the following:
Exercising your whole body to lose weight will eventually reduce fat in the facial area, too. In fact, it's very difficult to lose weight in just your face, and that's often the last place to thin out. Starting a steady exercise routine with cardio and strength training can put you on the path toward a thinner face.  Running, swimming, and biking are all great cardio activities. Plan to do one of these activities for at least 1/2 hour 4 times a week. Go to the gym and meet with a personal trainer to get acquainted with a strength training routine. Learn how to lift weights to work out all of your muscle groups. This reduces the amount of fat you store in your body and your face. Satisfy your hunger with fruits, salad and low calorie food items. If you are really serious about getting rid of your double chin, losing weight can definitely help.  Don't try anything restrictive or faddish.  Your change must be one that you can carry on for the rest of your life.  Small, consistent losses are what you should be aiming for and maintaining. Your diet should include plenty of fiber, fruits, vegetables and water.  See a nutritionist, dietician or doctor for advice and encouragement.

Summary:
Do general exercise. Limit your calorie intake.