Avoiding the Freshmen 15?

Constant diligence! Honestly that's what it comes down to. Don't become obsessive, you need to focus on your studies, but keep a healthy awareness about your health. It's great that you're already getting in the habit of walking everywhere and counting calories:)

Find a friend to keep you accountable too! For me that was the best way I found to keep in shape. I only got into weight training in college so I buddied up with a friend who practically lived in the gym. I learned a ton from him, and it provided a healthy sense of competition as well as an outlet to talk about classes and such. Consider your workouts "free time", not just another item on a to-do list or you'll resent it and slowly stop working out altogether. Take the opportunity too to try something new! I got really into salsa and tango classes my first semester. This way you're being active, meeting new people, and taking a break from school

Another tip too is to keep minimal snacks readily available. Those snacks should be healthy-Quest bars, fruit, granola, etc. Recognize if you're an emotional eater or a stress eater, and then be proactive about it! If you feel that you're getting stressed or bored and have that urge to snack, grab your roomate and go for a walk. In addition, I've run enough callouts and meetings to know that free food is a guaranteed full house. Knowing that, be smart going into those situations. I always ate beforehand so I wouldn't be tempted by the pizza and pop. Alcohol too is an easy trap I've seen a ton of people fall into. Two words: light beer. In all seriousness though, don't be dumb about binge drinking. All they are are empty calories and an invitation to bad decisions.

Hopefully that helps a bit! I just shipped off my little sister to college so I'd like to think I've got my spiel down haha Anyway, don't hesitate to PM me if you have any questions. Best of luck:)

I gained a lot of weight in my second year, and I genuinely now believe it was a combination of not sleeping enough, getting and staying too stressed, relying on ramen noodles (which I ate a lot of because they left me hungry,) and generally drinking a lot for anxiety. I did think that drinking accounted for all of it, until I stopped and my weight hardly budged. I would advise you to always get enough sleep and take up some adequate means of relieving stress.

Try making home cooked meals instead of going out to eat. Make chicken and beans and eat lots of fruits.And try to incorporate weights to your workouts.

The oatmeal is good - get the rolled oats and make your own though, with bits of raisins and brown sugar or whatever. You have more control over it. Run away from the Ramen, there are healthier quick/cheap options out there.
Something that will go far is having a time every day where you're being active - something that will stay constant regardless of your class schedule changing (so, if your classes are never earlier than 9, having 8 am being your always-working-out-time). Having a regular schedule and a regular wake up time that stays constant even on the days when you don't have class until 1pm will be super helpful.