Attend class daily, and arrive on time or a few minutes before class starts. The more you attend, the more opportunities you'll have to contribute, and you'll also be better-versed with the course's content as well as the types of contributions your instructor prefers. Arriving late disrupts the class, so avoid lateness when possible.
Come to class prepared with completed homework and reading assignments. Listen attentively during lectures and take notes. You can contribute to the classroom environment by setting an example with this type of conscientious behavior, and you're better equipped to handle classroom discussions when you understand the material.
Answer the questions posed by your instructor or other students and give your opinion during class discussion time. Don't be afraid to speak or ask a question. Other students probably have similar questions or opinions, and your instructor likely will be overjoyed that someone is volunteering to speak. Be prepared to back up your opinion logically and with evidence.
Respond civilly to others who disagree with your statements and encourage them to explain their viewpoints. Successful classroom contribution requires a tone of support and mutual respect. A classroom functions best when students feel free to explore ideas. Defend your opinions, but don't make it personal or get angry.
Exchange information with students who sit near you to create a classroom support network. Use these contacts to form study groups, work on group projects and exchange notes when someone misses class.
Offer help to other students who appear to be struggling with the material or completing an assignment.
Volunteer yourself when the instructor asks for favors, such as passing out papers or bringing materials for a classroom project.