This is one that has really helped me be more focused. Example: I am at my desk working away very deep in what I am doing and the phone rings. I can choose to ignore it and have voice mail get it or I can answer it.
      I decide to answer it. I must STOP what I am doing, CHANGE modes and Focus on this new task and START the new task of talking on the phone and giving that task 100% of my attention.
      I find that when I do this, I can be on target with each task that I do. And I find it easier to return to a task when I have delineated between them. In this way I get to concentrate on each task 100% and therefore I don't miss anything or have dangling details that can get lost, missed or forgotten.