First, a significant number of people must be potential members of a class, often referred to as numerosity. There must be so many potential plaintiffs that it is not practical for each to individually bring their claims. There is no magic number, as it is determined on a case-by-case basis. There must also be common facts or similar legal questions between the class members, referred to as commonality. The class representatives' claims must also be typical of those who are members of the proposed class. It is not necessary that their claims be identical, referred to as typicality.

Finally, the class representatives must be able to fairly and properly represent the class. The court must be convinced that the representatives are pursuing the interests of the class and not just pursuing their own interests at the expense of class members.