You may be totally intimidated by your professors, or you may be eager to meet them but not know what to do first. It's important to remember, however, that most professors are professors because they like teaching and interacting with college students. Talking with your professors outside of the lecture hall just may be one of the most rewarding aspects of your college career.
Go to class -- every day.
Many students underestimate the importance of this. True, in a lecture hall of 500 students, your professor may not notice if you're not there. But if you are, your face will become familiar if you can make yourself noticed a bit.
Turn your assignments in on time.
You don't want your professor to notice you because you're always asking for extensions and turning things in late. True, he or she will get to know you, but probably not in the way you want.
Ask questions and engage in discussion in class.
This can be an easy way to have your professor get to know your voice, face, and name. Of course, only ask questions if you have a legitimate question (versus asking one just for the sake of asking) and contribute if you have something to say. Chances are, however, that you have plenty to add to a class and can use that to your advantage.
Go to your professor's office hours.
Stop in to ask for help with your homework. Stop in to ask for advice on your research paper. Stop in to ask your professor's opinion about some of the research he is doing, or on the book she's talked about writing. Stop in to invite him or her to your poetry slam next week. But try to stop in!
Go to an event where your professor is speaking, or to a meeting for a club or organization your professor advises.
Your professor is most likely involved in things on campus other than just your class. Go hear him or her lecture and stay afterward to ask a question or thank them for the speech.
Ask to sit in on another of your professor's classes.
If you're trying to get to know your professor -- for a research opportunity, for advice, or just because he or she seems really engaging -- you most likely are interested in similar things. If they teach other classes that you might want to take, ask your professor if you can sit in on one of them this semester. It will indicate your interest in the field; additionally, it will undoubtedly lead to a conversation about why you're interested in the class, what your academic goals are while you're at school, and what interested you in the topic in the first place.