The book is the best place to understand it, in my opinion. There's plenty of summaries, but the book is good. But if you take nothing else: next action. When

The book is the best place to understand it, in my opinion. There's plenty of summaries, but the book is good. But if you take nothing else: next action. When planning a list put the next physical thing you need to do (call, draft, debug a specific routine, etc), not abstract concepts.