Wearing eyeliner and mascara makes the eyes look larger and draws attention away from the chin. Minimize attention to your lower face by wearing neutral lipstick shades.
Go for a long bob. This classic cut looks great on people with larger chins. It should stop an inch or two below your chin line. Get an angled haircut. Have the longer hair in front, shorter hair in the back. The longer hair in front reduces the size of and draws less attention to the chin. Try layered waves. A full hairstyle balances the face and draws attention away from the chin.
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.
Avoid restrictive or fad diets. Instead, make small, healthy changes that you can sustain for the rest of your life. Your diet should include plenty of fiber, fruits, vegetables, and water. See a nutritionist, dietician, or doctor for advice and encouragement.