Now that we have a thorough understanding of the academic side of what drives emergency department (ED) operations, it’s now time to turn toward examining best practices in emergency medicine. In this and the following two chapters, we will look at these best practices in the context of the three fundamental time intervals in the ED—door-to-doc, doc-to-dispo, and dispo-to-departure. We will discuss these intervals in the context of what we have learned thus far about Lean thinking, queuing theory, and the theory of constraints.