In this paper we present an onboarding checklist for Research Computing and Data (RCD) Professionals. RCD Professionals are individuals that work with researchers, students, and industry staff on the computing and data needs associated with their work or study. This work was supported in part by a National Science Foundation grant: OAC-2100003, an NSF-funded Cyberinfrastructure Center of Excellence (CI CoE) demonstration pilot — RCD Nexus. The authors would also like to acknowledge the broad community of volunteers who have contributed in workshops, working groups, and other activities over many years.