Open Question: Healthy way for teenager to loose weight?

I'm 12 gonna be 13 at the end of July 2010 I'm 5'3 144lbs. I want to be in a bikini. Which I do look okay in one now like I can wear one but I wanna look great. So any exercise plan or anything will help. In my backyard I have a pool, swings, and a trampoline. Plus I have a huge yard. I run laps sometimes. I also have a bike. So any plan will be good. No food recipies pls. I will just watch wat I eat Does anybody kno my bmi