What is a good diet?

okay so im 15 and this summer I plan on going on a diet because I want to lose like 40 pounds.. and if I do I get my belly button pirced and a really cute bathing suit from victoria secrets... I need to know a good diet please help.

Work out a bit eat a little smaller portions and cut down on the fatening foods.

Oh, and stop the pop drinking. That's what I did, and I feel so much better.
Drink a lot of water. And after you've done some dieting, try even more. Get your body used to it... Start running/ working out longer.