A framework for using checklists to improve outcomes by acting and thinking more consistently in an increasingly complex world. Drawing on examples from surgery, aviation, and construction, the author shows how checklists reduce errors of omission—missing critical steps under pressure—and errors of ineptitude—failing to apply what we already know. He explains two types of checklists and when each applies: “do-confirm,” where you perform tasks from memory and then verify them, and “read-do,” where you follow steps line-by-line in high-stakes or unfamiliar situations.