I used to be 'big', but after a while, I got really skinny and tall. You just need to exercise a lot. I love playing sports, and I like going to the gym too. Also, you need to eat really healthy. I've tried my best to avoid junk foods like pop, chips, and etc. I eat fruit and other healthy foods.
One thing you DON'T WANNA DO is not to eat. You will just get anorexia, which is a horrible disease. Also, if you don't eat, you're eventually gonna eat, right? As soon as you start eating normally again, you'll gain your weight back. So just eat really healthy and exercise a lot.
Patience is also key. You don't lose 10 pounds in 30 minutes. You need to spend some time. After ~1-2 years, if you don't notice any difference, then take it to the next level.