I've been doing GTD for over a year now, & I still can't get the hang of contexts. I put things that must be done on my calendar, & if I finish those I don't seem to look at my contextual lists except for errands. It's frustrating because I find I don't do things unless they are on my calendar. Part of it is because I don't find that my daily plans center around a location where I can plug into a list. I could just as easily be in my office as in my car or on my handheld where most of my lists reside. Ugh. I fear I'll never really get this methodology.