I am at an unhealthy weight for my height and Age and need tips?

I am 16, 5'5", and weigh about 225lbs. How much should I weigh for this age and height? Besides A good diet and exercising whats some other tips for loosing weight? like what are some good healthy, low fat snacks. foods, and meals? And like I know I am suppose to drink a lot of water but because I have a dehydration problem I was told to drink gatorade or various drinks with electrolytes. So any other information that I can get to help loosing weight would be great:)