Good answer. I agree, eating is key. Up to about 25, you can probably pretty much eat what you want. After that, you have to start keeping track of what you eat. Being active is the second most important thing; it's not easy at first, but it gets easier if you keep doing it. If you're like me, some kind of positive reinforcement is extremely helpful; I'm using Wii Fit to keep track of my weight and BMI. That way, exercising and being healthy starts to feel like playing a game because you can see your progress, and you can immediately see when you start to slack off.