Include expected and unexpected commuting, research, homework, and personal obligations. On average for every hour of class time there are three hours of preparatory time required. Plan this in advance. This is not only a good way increase your interest presently, it can also lead to the possibility earning a minor or double major, sometimes with little extra effort. Chances are others in the class have the same question.
Answers are usually better in general with better questions.
Participating and contributing contributes to a healthy lifestyle, and a great way to make life long friends. It also helps you in time management.