Your best bet is fulfilling the food pyramid. It gives you exactly what you need, and you won't go hungry. Meat helps build up muscle, veggies are vitamins and some are called calorie killers because digesting them actually takes more energy than they give, dairy is calcium for your bones, grains are quick energy, and everyone needs some sugar. Your diet wouldn't be complete without it. What you have to look at is portion control and making sure you have everything in there. And I wouldn't suggest eating right before class.
Eat healthy, like eating salad, some meat here and there. As for drink, drink mostly water, and gatorade, or anything you consider healthy.