1. Gotta Keep Moving: Why drive two blocks? Walk there, if it's safe. Crowded parking lot? Forget it...park on the far end, and walk - if it's light outside. Talking on the phone? Walk around. Clean your room as you analyze what everyone said at the party. (Productive gossip, I call it.)
CAUTION: Do get plenty of sleep at night, and DO NOT EVER EXERCISE OR "KEEP MOVING" TO THE POINT OF EXHAUSTION!
2. No Couch Potatoes, Please: Watching TV? Surfing and Chatting? Are you accompanied by a bag of chips? Watch out! Sitting and vegging occasionally is great - - but for many hours a day, it's no good. Ditto for the chips - a few are cool. A bag - NOT. Get some fresh air and some non-virtual exercise. And an apple wouldn't kill you either.
3. Find a Sport You Love: ...and stick with it. Shooting hoops, running, kick-boxing - anything that you enjoy that makes you move your muscles. Not only will this favorite activity keep you in shape, it will also keep you friends with your body. When you see how much your bod does for you, you may appreciate your muscular legs. Super models don't play football or field hockey. Healthy people do.
4. A Few Good Meals: DO NOT STARVE. It's simple. If you deprive your body of food, it will eventually deprive you of proper function. You should not be consuming entire boxes of cookies, either. But there is a happy medium - well-balanced, healthy meals that fit your eating style. Do you prefer five or so small meals - an apple and a yogurt, or a salad with some bread - to three big ones? That's fine, too. But you need to get enough carbohydrates, fruits and vegetables, meat or fish or poultry, and dairy products - all of them, every day. If you are not sure about what's right for you, consult a nutritionist. They love talking about this stuff. (It's more than a job for most of them...)
5. Look Out for Number One: Be good to yourself.
Get some sleep, for God's sake.
Take care of your skin. Don't color your hair so many times that it falls out by the time you're thirty.
Don't smoke. Don't do drugs. Don't abuse alcohol. Surround yourself with supportive people. Screen out the non-supportive.
Treat yourself like you would treat a boyfriend or girlfriend with whom you are in love.
If you don't, who will?