For the first two years, everyone is part of the General College and you mostly take intro classes and classes that fulfill your perspectives to give you a well-rounded education. One cool thing is that freshmen are encouraged to take a freshmen seminar, which caps at 20 students and is on a random interesting topic, so you really get to know a great professor and a great group of students. All language classes and intro English classes are also really small. Other classes vary, with the big lectures like Econ, Chem, and Bio having about 400 students in them. I had some great classes my first two years (The World Since 1945, History of the New Testament) and some not so great classes (Intro to Statistics). Some people hate having perspective requirements (i.e. a science w/ a lab, a philosophy, an old history, etc.), but I think it's important to be well-rounded, and there are a lot of course offerings to fulfill each requirement. Plus, you can get out of a lot with AP or transfer credit. For example, I never took a single science in college, because I got credit with AP Biology in high school.
How much you study really depends on your major. Get ready for long hours in the lab and long hours studying if you are a science major. Get ready to write a lot of papers if you are majoring in some of the humanities like Poli Sci or History.
My major at Carolina was Business Administration. Business is different from a lot of majors on campus because it is a professional school, and you have to apply your sophomore year to get into it. The average GPA is 3.5 to get in, so it's definitely pretty competitive. Once you are in, you take the vast majority of classes at the bschool on south campus, rather than on main campus where most classes are. A lot of people have a love/hate relationship with the bschool. Drawbacks of the bschool: it's a lot of classes and a lot of work, so you don't have as much time to spend on main campus any more; it tends to be frattier than most majors; it's slightly more competitive since a lot of people are out to get the top jobs at the investment banks and consulting firms.
In general though I loved being in the bschool. For one thing, only about 330 people are accepted into the bschool, so over the two years, you get to know a lot of the same people really well. The business school is its own little community within UNC (its own cafeteria, computer labs, campus, etc.), which I loved. The facilities are great; it's definitely one of the most high-tech, comfortable places on campus, since the buildings have only been around for 10 years and because rich alumni give us a lot of money. The best thing though is the professors. I took 16 or so classes at the bschool over my junior and senior year, and only in corporate finance did my professor not get to know my name. In every other class, there's a lot of class interaction, and the class sizes are pretty small, so you get to know your professor pretty well. Plus, these are never TAs; these are real professors which awesome credentials. I seriously loved almost all of my professors. They are very encouraging and open to meeting outside of class, and they genuinely care about you, offering career advice and staying in touch with you after graduation. The business school is more oriented toward job placement than most majors, since a lot of companies come to recruit business majors. This is especially true for business students interested in things like finance, accounting, and consulting. The bschool offers workshops and mock interviews and all kinds of things to help prepare you.