Whatever you do, do not try to become anorexic. That is not the good path. You will be doing all this work in vain, because you'll end up eating again, whether it's your own choice or it's been forced down your throught at an institution.
Instead, do this:
Eat a good breakfast, a good lunch, and a light dinner.
Try not to snack much in-between meals, but if you must then make it healthy things like fruits.
Forget about chips, ice cream, chocolate, etc. If your going to lose weight you have to be really dedicated.
Exercise. Exercise. Exercise.
Swimming burns calories like crazy. Also, try spinning, running, soccer, tennis, etc. Try doing at least 30-45 minutes of one of these every day.
Make a playlist on your iPod that makes you want to dance. Lock yourself in your room and dance BECAUSE no one is watching.
Walk for half an hour to one hour every day. It will help set your body to a tone.
Drink a lot of water. It will NOT make you bloated, but it will help you loose weight.
In order to lose weight, you have to burn 500 more calories than you consume a day. Do the math. Record everything you eat and find out how much calories it has (try calorieking.com) and compare it to the amount of calories you burned that day.
Don't, don't, don't, don't skip meals. And don't become anorexic or bulimic. Those girls don't look pretty anyways. They look unhealth. They look tired. People don't like a sad girl that's always tired. Remember that.