I've just finished reading the book, am brand new to GTD, and the one thing I've had the most difficulty wrapping my head around is how to manage the multiple actions of a project.
For example, I identify a new project and add it to my Projects List. Over time I will identify multiple actions that need to occur in order for that Project to be completed. The actions may occur to me all at once in one thinking session, or they may occur to me over the course of a few days. In order to "get it out of my head RAM", I want to immediately record them.
This is where I start to have difficulty. Only the true next action goes onto @nextactions. And so the result is that these various "other" actions are now scattered across multiple lists i.e. @phone, @computer, @errands, @office, @home, @agendas, @waiting, etc.
So when I need to determine what the true "next action" is for that project, I need to scan through each and every one of the above lists, locate the actions that apply to the project, and holding them all in my head, decide which one becomes the true next action!?
And some actions don't fit on any of my lists, and therefor I don't know where to record them. I guess an @misc? but that's probably too dangerous!
My intuition tells me that I'm just not getting this, or I've misunderstood some detail in the book, or the various web articles I've read ... and that's why I chose this topic "Feeling Dense and Not Getting It".