See your doctor. There are medical conditions that can cause you to be heavy. Also, it's a good idea to have a physical before you start ANY weight loss.
1. Watch your diet. Limit starches (breads, pizza, potato). Eat lean meats, fish is good - but don't fry it! Make sure that it is a balanced diet.
2. Eat breakfast! It gives your metabolism a boost in the morning so you burn more calories throughout the day.
3. Limit your snacks.
4. Get up and outside. Turn off the XBox and TV. Get MOVING so you burn all those calories. It is MUCH easier to lose weight at 14 than it is at 40.
5. Keep hydrated - drink WATER. We tend to eat more when we're hungry so keeping hydrated will decrease your hunger.
6. Remember, it's OK to OCCASIONALLY eat something you shouldn't.
Here's some motivation for you. Not only can you lose weight by doing this, but it will also make your penis appear bigger. Any fat around it "hides" it so it looks smaller than it is. Want a bigger penis, lose weight!