Groups are a basic social structure, and both within and outside the academic world they form and reform in a variety of ways for multiple purposes. On a college campus, students gather together in groups for all sorts of reasons ranging from clubs and committees to athletic teams and sororities. While students form groups naturally and easily outside the classroom, forming groups within a course can be an unnatural process. Yet for collaborative learning to be successful, it is important to form groups that can effectively and efficiently accomplish the goals of the assignment. In this chapter, we provide advice about group formation in three key topic areas: group types, group size, and group membership.