Command selection is probably one of the most ubiquitous and important tasks with interactive systems. It consists in offering to the users one or several methods to select a command among a set of commands. These methods include menus, toolbars, keyboard shortcuts, etc. In this chapter, we first categorize and describe the main methods for selecting commands. We then discuss how certain platforms introduce opportunities and constraints regarding command selection. After that, we detail key features that designers should consider when designing methods for selecting commands and how these features can be adapted during the interaction. We then review how to improve performance when selecting commands. Finally, we highlight three main challenges for future work on command selection.