In this paper, three types of case study, which are fully exploratory, partial exploratory, and confirmative case study were firstly classified. Then, roles of literature review, interviewee selection, and interview question design are investigated, as well as their implementation. Each of these is explicitly explained by a following example. Finally, similarities and differences of the three type case study are compared. Six common points of context preresearch, interview time and the number of interview questions control, notices of interviewers, development of interview questions, data collection procedure arrangement, and theoretical saturation testify are illustrated. At the same time, using typical events or practices as interview objects are proposed.