In total, I gained the college 40-50 (thank goodness I was on the bottom edge of healthy weight before I started there!); a buffet cafeteria combined with poor eating habits made for a terrible combo. You have my sympathies for your potential gain.
My suggestions, after having shed off a little over 30 lbs this past Sep-to-Sep year, include the following:
* developing an increased awareness of the calories you consume versus a reasonable approximation of the calories you expend; this includes looking comparative at the nutrition labels of the food you're likely to buy
* moderate your food intake and make yourself aware of how many servings you've had / intend on having
* be aware of the caloric intake of any booze you may consume
* replace "try to get to" with "go to and use"
* cardio, cardio, and cardio
* engage in physical activities (sports and hobbies) with your friends to enjoyable burn calories
* walk for twenty minutes instead of driving for five, where possible
* make sure that you're not confusing your lean muscle mass gains with your potential increase in excess fat (in terms of your weight)
* find alternative exercises that can replace the ones your school gym lacks
* beware takeout ("fast food") and their presumed serving sizes
* structure your meals-per-day and develop some degree of dietary discipline