Getting Things Done (GTD), created by David Allen, is a productivity method built around capturing every task and idea in an external system so your mind is free to focus. The workflow has five stages: Capture, Clarify, Organize, Reflect, and Engage. Capture funnels every open loop into a trusted inbox. Clarify asks, for each item, whether it is actionable and, if so, what the next physical, visible step is. Organize places items in lists (next actions, projects, waiting for, someday/maybe, reference). Reflect is the weekly review that keeps the lists trustworthy. Engage is simply doing the work—the state Allen calls "mind like water." Inbox consolidation—routing all captures to a small number of trusted inboxes, often one—turns processing into a predictable habit, and a regular drive toward inbox zero keeps unprocessed material from accumulating.
GTD draws several useful distinctions. A project is any desired outcome that requires more than one action; a single task is one observable action you can complete in one sitting. A "next action" is the very first physical, visible step toward a project, with no ambiguity about what to do, and a Horizon 1 review confirms that every project has a defined next action right now. The two-minute rule says that if an action takes under two minutes, do it immediately at capture time instead of deferring it. Non-actionable items are routed to trash, reference, or someday/maybe; items delegated to others go to a "waiting for" list so nothing slips through while you are not the driver; the inbox triage stack works through each item with a small set of standard questions (actionable? project? two minutes? delegate?). A trusted system is one you can rely on to hold your commitments and surface them at the right moment; when it is not trusted, you start re-remembering things in your head, capture less, and eventually abandon the tool.
GTD also describes a six-level hierarchy of goals: runway, projects, areas, goals, vision, and purpose. Reviewing at each horizon is part of a multi-layered cadence: daily for the inbox, weekly for projects and a trigger list—calendar, email, notes, projects, waiting for, someday/maybe—and quarterly or annually for vision and purpose. Horizon 3 thinking asks you to evaluate some captures against long-term, multi-year direction rather than only today's tasks. A "learning project" in GTD is a project whose outcome is acquiring a skill or understanding, broken into next actions like reading chapters, summarizing, and teaching. A pre-mortem note imagines that a project has already failed and lists the most likely reasons before starting, surfacing hidden risks; a decision log or decision journal records important decisions, alternatives, reasoning, and a later follow-up comparing actual versus expected outcome. A trigger note—a checklist that activates when a specific kind of project starts—lets you turn recurring steps into a reusable file rather than a recurring task.