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For knowledge workers, there is a lot of work to do defining our work before we can start actually doing our work. The 5 phases of workflow is the GTD model for capturing, defining and doing our work.
Many mobile phones and dedicated dictation machines allow you to capture thoughts as you have them in the form of voice notes. A great collection tool to have with you at all times so you never have to remember anything again (as long as you remember to process the notes just like any other inbox).
The practice of setting aside dedicated time (typically a couple of hours) to make sure your system is clean, current and complete. David Allen regularly cites this as the critical success factor for GTD.