Are you going to be eating at a dining commons? Avoid the potatoes at every meal, and the desserts. The Commons will have some healthy or vegetarian alternatives; go for those rather than dishes with lots of gravy or pasta.
They’ll have fresh fruit, go for fresh fruit instead of something high in carbs and or fats. Grab an extra apple at lunch for an afternoon snack, so you don’t end up at a vending machine.
And if you are a drinker, don’t go to crazy with the beer. I went to U.C. Santa Barbara, one of the top party schools in the country. It was a bit disappointing to see a beautiful freshman girl that was in great shape the previous fall walking around with a beer gut six months later.