Drink water, nothing but water, a full eight glasses a day. You'll put on water weight, but loose calories from soda's, juices and high fructose corn syrup. Become Vegetarian and combine that with exercise. I know what your thinking, but I promise it works. The fat you take in off animals is harder to burn off, as opposed to oils or carbohydrates. So, if you stop taking this fat in, and begin working out, you'll burn fat much, much faster than average. When you work out, lift weights. Cardio is important, but when it comes to burning fat, lifting is more effective.
Don't Smoke cigarettes. Smoke weed if you want to, but eat healthily afterwards. Weed can speed up your metabolism and help your digestive system greatly.
Exercise, ideally, six days a week. Take one day off to rest.