Where would we be without them? Teaching assistants (TAs) make it possible for us to deliver high-quality large-scale computer science courses with relatively few faculty. Though their responsibilities vary by institution, TAs often play a crucial role in student learning. The use of teaching assistants in computer science courses is a common and longstanding practice and, yet, little has been published about how to choose the best TAs among those interested in the job. This paper describes the development of an interview rubric in use by faculty teaching a large introductory computer science course to score applicant responses in a formal in-person 30-minute interview. We describe the motivation behind developing such a rubric, the initial development process, its refinement based on feedback provided by students about their TAs, and the preliminary results of implementing this hiring system.