Peer instruction, a form of active learning, is generally defined as an opportunity for peers to discuss ideas or to share answers to questions in an in-class environment, where they also have opportunities for further interactions with their instructor. When implementing peer instruction, instructors have many choices to make about group design, assignment format, and grading, among others. Ideally, these choices can be informed by research about the impact of these components of peer instruction on student learning. This essay describes an online, evidence-based teaching guide published by "CBE--Life Sciences Education" at http://lse.ascb.org/evidence-based-teaching-guides/peer-instruction. The guide provides condensed summaries of key research findings organized by teaching choices, summaries of and links to research articles and other resources, and actionable advice in the form of a checklist for instructors. In addition to describing key features of the guide, this essay also identifies areas in which further empirical studies are warranted.