ive been working out for about two years now, and well most of the advice given here is crap, no offence, its always 90% diet. i never had a weight problem so i dont know much about loosing it, but if you want some real help goto
http://forum.bodybuilding.com/ . theres a weight loss section, and a teen section. post your weight, height, what your goals are and there are plenty of real experts there to help you.