Walks...watch what you eat... lay of the cakes and donuts...and go easy on the pepsi and or coke... eat plenty of veggies... take smaller portions of food... take up a sport.. such as karate or kick boxing... get those muscles in shape !.. Good Luck !
Ashley dear, just eat a well balanced diet, veggies, fresh fruit , lean protein , and dairy. Don't eat things that say low fat, they have added sugars. Exercise, jumping rope is fun at any age. Just be active. You will be fine!!!!
As long as you look healthy, you're fine. If you're SUPER skinny you might want to gain more weight. And: Exercise and avoid foods that contain a lot of calories. You're a teen right? I'm a teen too. Gaining weight is normal for teens. :)