Diet. Exercise. Diet of fruits, vegetables, nuts, beans, lean fish and very little dairy, non-whole grain bread (get from whole foods not your regular grocery store - they lie about whole grains), meats. No fried food or processed snacks. Eat out less - too much salt. Cook at home or learn - its healthier and you see what's going in your food. Stay away from the horrible american diet. And exercise daily!
Caloric balance. The way to lose weight is to burn more calories than you take in. That means eating less calories (especially in fried, fatty foods and simple carbohydrates) and burning more (exercise, weight training, etc). Don't neglect lifting weights - lean muscle burns calories 24-hours a day!