I’ve read the book from David Allen a couple of months ago and started to implement the methodology right away. For me it was rather easy to do this, as I already had the tools (mostly software) to create my lists and planning tables. I’ll describe a short version of this method, however I highly recommend that you read the book for detailed explanation and real life examples. If you would like to read more details on the software I use please read how to be efficient.
Get things off your mind so you can focus on the action which you’re actually doing. Your mind should not wander. This will help you to be in the flow.
This method is quite simple, however it might take a few weeks until you get used to it and build your own system. I’ll describe my way to do it, however create your own way to implement it in a way which makes most sense.