Diet & exercise. You need the diet part to go with the exercise. Make sure you exercise at least 30 minutes a day, don't skip meals, avoid soda, juice, dairy, alcohol and fried foods. Eat a healthy well balanced diet! Also water, organic vegetable broth, green leafy vegetables, natural pickles, apples are great to fill you up so you dont feel hungry and they are very low in calories.
Use more calories. Anything that uses energy (calories) will help one lose weight, as long as he doesn't eat or drink back more calories right after the activity. Examples: if walking, take a longer route; use stairs instead of elevators; take multiple trips to and from the car when unloading groceries; park a block from school and walk there with the kids; at home, skip dessert and go walk around the block instead.