Apart from all that stuff people posted.
1) You MUST keep doing it. Do not do something for a week, assume its working then splurge.
2) Walk/Run. Just do it. You don't need to go to a gym, that is to build muscle and maintain strength. Sure the gym has equipment that helps you "shed" pounds. But just run or walk. Maybe start walking, then to a slow jog and go from there.
3) Portions when you eat. If you stay up late and have a craving, don't give in. Find yourself a "snack" food. For me its almonds. I hate them, but it prevents me from wanting to eat something ridiculously fattening etc.
4) Keep a steady pace keep it up and keep doing it. For instance, when you run, you'll feel great for the first few weeks then drop off. Push through the low point then you'll level again.
For me when I run I get a natural high from it. I love it. I'll run for an hour, or maybe more if I feel like it. I bring a friend, we can gossip and talk while doing it. Play a sport (you're in high school right?) I played soccer all throughout high school, practiced every day and destroy myself. But it was great. Now since I'm in college and I run at least 3-4 times a week.
So in conclusion: Watch what you eat. Eat less. Less is more, its true. Dropping soda's is easy too. Then you'll be good. You need to put your mind to it, have something to motivate you. When you look good, you'll feel good and everybody will notice. Then you can be that hot guy.