What are some ways to get a nice, fit body before Summer?

I'm fifteen and Summer is just around the corner. I'm not bad looking in a bathing suit, but I'd prefer to look better. I have that so called "pooch" at the bottom of my stomach. But the top of my stomach is tight. I play softball and I'm a cheerleader so I'm pretty fit. But those workouts just don't seem to cut it. I have jiggly arms, but I have a lot of muscle. I have big thighs but those are also muscles. I want them tightened up and toned. And I want a tight , as odd as that sounds. So how can I tighten up all these muscles and get a nice flat stomach in such a short amount of time? Please and thank you! :)