Last, but not least I walked everywhere and I mean everywhere. I never got a chance to gain weight without a car to drive me around everywhere. Even when I had my car on campus, it was so hard to find parking, I walked.
You can also join an organization that is active. It is easier with a group to stay healthy!
Be prepared! There is nothing worse than getting super hungry and finding yourself with vending machines and fast food as your only options. Always carry non-perishable, healthy snacks like almonds, protein bars, and coconut water(many times being thirsty is mistaken for being hungry. I definitely recommend allowing enough time in the morning for a hearty breakfast that includes protein. Lastly cooking for yourself is great especially when you have leftovers. Soups, lasagna/pasta, and grains keep for several days and are filling meals without lots of prep time. Bon Apetit!