Incoming freshmen, like a lot of people mentioned, have often moved into campus about a week earlier, and have spent the last several days being part of organized activities intended to help familiarize them with their surroundings, put them in a good mood about the campus and the school, break the ice with other students so that they find a few friendly faces to start off with, get them over any melancholy from Change, and so on. There will usually be socials-- ice cream sundaes or floats-- visiting the stadium for a spirit rally-- you'll often be assigned to a Small Group to travel and lunch with so you don't get lost in the crowd-- frequently some kind of live entertainment and food several evenings. At my undergrad, the Alpha Phi Omegas (service fraternity) were usually tapped to be the small group leaders, although they weren't allowed to advertise themselves as such.
At my undergrad, it was mandatory for freshmen to live on-campus in the dorms. You weren't allowed to live off-campus until your sophomore year, but some of us-- like me-- who didn't have vehicles-- like me-- stayed in the dorms all four years. The first year, we got assigned a dorm and a roommate at random. If you're sticking around for your sophomore year, we had to find our own roommates and apply for the dorm we wanted, because we weren't allowed to stay in the freshman dorms. If you didn't have anyone you liked enough to live with, they also had mixers where other mehhh people could find a warm body to pair up with and claim a room together.
Class registration already happened. Because you're a freshman, you're at the bottom of the priority list. At our school, seniors and honor students got first whack at the schedule back in, say, April; then juniors; then sophomores. The logic behind it is that the seniors are very limited in which classes they need to build their schedule, so they want to make sure those last classes in the right time slots don't get full before the seniors get a chance to sign up. The further down you go, the more flexibility people have in their schedules in being able to make things work out, so their priority is less. The incoming freshmen are total blank slates for their classes, so it's easiest for them to figure out something to get their first 9-12-15-16 hours. You have an advisor, and you're not allowed to sign up for anything that first year without their say-so. At my undergrad, high school seniors can't register until they are (a) accepted, and (b) made their deposit, and (c) advised. Advising takes the holds off your account, and you're able to register by phone or online if you can't register in person. Acceptance letters often go out in December/January, so April/May signups are pretty realistic.
By the time you get to the first day of actual class time, you're relatively familiar with your surroundings, but if the campus is particularly sprawling, it can still be difficult to find the right building within the timeframe every day that first week. It can be like "Uh... I know I found my building with no problem on Tuesday... why am I so mixed up on Thursday?"
Lots of consulting the schedule and/or the map, and lots of paranoia that you've spaced out on the wrong class, or that you accidentally double-booked two classes for the same timeslot, or whatever, until your routine becomes embedded. At our university, we were generally MWF and T-Th classes. MWF were 50 minutes, and T-Th were about 80 minutes. Most classes were 3 hours towards our degree; language classes were 4 hours towards our degree; science was usually 3 hours with a lab for an extra fourth hour. A full-time undergrad student is at 12 hours, but someone who's double-majoring is going to take as many classes as possible (and transfer basics from the summer at the local community college or from high school dual-credit courses) in order to graduate on time.
In the classroom, the first day of class is pretty much going over each professor's ground rules, office hours, and syllabus, peppered with lots of anecdotes about former students of years past. The professor might say something like, "If it's more than 10 minutes after the bell rings, don't even bother disrespecting me by coming in late." Or, "I don't care how hot it is outside, I don't want to see anyone wearing halter tops in this class, do you understand? I remember there was this one girl who wore one, and we were in the middle of a test, and she decided to untie the neck on hers. It was really distracting to everyone around her, and I don't need distractions, period." Or, "These are my office hours. You can come by if you want to discuss your grade. But don't try to bribe me. There was this one kid who came in with rotten grades and he asked if he could have an A and he took off his Rolex and left it on my desk. And I'm like, 'Hey, don't forget your watch on the way out.' Because if I'm going to take a bribe, it had better be enough to allow me to retire, because I won't be able to work in my field again. So don't bother trying, okay?'"
For classes that involve composition or creation, your professor might ask you to write down the subjects of different things you did (papers written, art made, whatever) in high school. They'll cross-check it against future work and get mad at you if they think you've recycled bits of high school work for any of their classes. And then they'll write nasty notes. But a first-day person doesn't know that part yet.
If you have a particular real-life school in mind, definitely read up on their student handbooks for their specifics about what classes are necessary to graduate with a double-major BA in Archaeology and Fine Art. You can look at their maps, and their registrar schedules, and other Incoming Freshmen information packets to get your details right.