First, freshmen travel in packs, "The Freshmen Heard" is what the upperclassmen at my school call them. They walk in groups of at least five everywhere on campus. To the caf, to town, back to the dorm, etc.
Another give-away is that freshmen are the only ones to wear their lanyards around their neck for the first week of school. While many college student have lanyards they don't carry them around their necks nor do they let the lanyard hang from a pocket. It seems cool I know- I did it my freshman year as well.