Exercise. Run, bike, lift weights... anything that burns calories and gets your heart rate up. Burn more than you take in and you'll be golden. That's really all there is to it.
Probably need to lower the crap I'm taking in then, I ride my bike everywhere and do a bit of sport as it is. Best I stay away from the Food Folder, you clowns cook up some tasty looking death meals.
If you're already riding your bike around everywhere and at least getting in some exercise, then you're off to the right place. But you start with food, and I highly suggest taking a look at your diet. Immediately cut out all fast foods, and start making smarter decisions. Instead of soda, drink water or at least diet soda. The guys in the food folder are at least making their own food, and this is going to be ten times better than ordering out. You're going to need some calories if you work out, though. There's got to be something there to burn off. There are a lot of bad calories that you can eliminate just by making intelligent decisions and simply looking at what you eat. Be conscientious about what you shove into your face.