How to Work
The way I intrepet it is this:
Under the methods of GTD you are either:
Working off of your calender or next actions,
Doing work that comes at you during the day
(only after you compare it to your work inventory in NA's and Calender)
Or you are cleaning up your inbasket and turning your STUFF in to Projects, NA's etc.
This sums up the GTD Kung Fu that goes on with every office worker during the day. Inputs (emails, voicemails, delegations from the boss) are stacking up in your collection buckets (email box, inbox). As long as it is in a trusted bucket, you can feel good about working doing predefined work (GTD). If you are interrupted with something that cannot wait, this is doing work as it shows up.. you are deciding that this is now the most important thing to do. A key thing to do during "interruptions/work as it show up" in my experience is just throw whatever you are working on back in to your own in basket. Once you get good at this you can no longer be bothered by interruptions.... you have a safe guard that allows your brain to refocus with out losing where you were. You can safely put things aside and give people your complete attention.
the other idea is when you arent cranking down NA's (predefined) or taking notes from your boss in the hallway about the website rebuild (ad hoc) you are cleaning up the collection buckets of your life and defining and deciding what it all means to you.
The reason why these methods works so brilliantly is that, once learned, the user can really manuever with the most flexibility. It is truly the best systematic way to organize your day. I am still an amateur in a lot of ways, but when the heat is on and 3 people need to talk to you, there are emails waiting, and there are 2 proposals on your desk.. it truly is the fastest way to get the most done and feel good about whats not getting done.