Well first off how tall are you? That's a big deciding factor in proper weight, 125 is a different situation for someone who's 5' as compared to 5'9". Also list an average day of what you might eat and drink.
For example if you 5'6, you want to lose 5 or 7
pounds, and you're eating kind of healthy, it may be as simple as eating a little bit more veggies, switching from white to whole grain breads, cutting out soda and junk food (or limiting it), and taking a 30-45 min jog 3 times a week.
MyPyramid.gov - United States Department of Agriculture - Home you can sign up and track your caloric and nutritional intake here. The food choice's and their
calories are general but it gives you a decent idea without going too crazy with food labels and a note book.
Be totally aware you are young and growing, so logic would tell me not to cut your caloric intake below 1500-1600 a day, I am not a doctor however. If you're cutting a lot of
calories you need to tell your parents you want to talk to a doctor or nutritionist about this.