Feel free to drop by whenever you have questions. Especially don't be afraid to talk to your freshman advisors . It's very important not to view your professors as aloof and unapproachable. Don't think of them as only existing to give a few lectures and hidden away for the rest of the week. Don't make the mistake of never seeing your professors outside of class.
Office hours are there to be used.
I often find that there is a misconception about office hours. Some students feel that they are only to be used if they have a personal problem and need to talk to the professor. That's not at all true. Office hours are there for tutorials . If you are having trouble with homework, completely lost about a question on the last test, or have a question that didn't get answered during lecture, go to office hours.