Office hours are attended by hundreds of students everyday, so don’t be nervous or intimidated. Professors are people too, and they love when students drop by to learn more about their field of study.
When you arrive, be sure to introduce yourself and tell them what course you’re in. In the beginning of the semester, drop by simply to introduce yourself. You can even just chat about why you decided to take that particular course.
At any point during the semester, drop by and ask a question about the material, no matter how big or small. Feel free to go a little off topic during office hours: ask your professor’s advice about a course-related problem your student organization is facing or their research.
Office hours work best when they are a conversation about course material and related subjects. Remember that it’s okay to get a little personal: these people might be writing your recommendation letters one day!