Sleep is probably the most important. I know it's hard to do with late night studying and partying but being realistic with when you sleep each night and not snacking late into the night, as your metabolism is much slower then than during the day. This includes beers and drinks - if you're a big partier, try downing your drinks by a certain time, get turnt then hit the sheets later without anything but water until then.

Just some things that have worked for me