I have just finished a book that should be a companion volume to GTD. I found myself doing the whole GTD system but still putting off the next action (as I have read others on this board do as well). I know from my past performances that I'm a chronic procrastinator.
So I just read The Now Habit: A Strategic Program for Overcoming Procrastination and Enjoying Guilt-Free Play. Awesome book! He covers some of the same territory DA does in GTD. But this book is more focused on overcoming the reasons for our procrastination (i.e. procrastination is a symptom--not THE problem). It gives great practical steps and minimizes the psychobabble.
One of his approaches is called the "Unschedule." You schedule all of your "have-tos" like eating, sleeping, appointments, etc. Then you schedule all your fun stuff like exercise, watching TV, reading, going out, etc. Then with the space left over you follow a few principles like not working on your procrastinated project(s) for more than 5 hours per day, not working on your procrastinated project(s) for more than 20 hours per week, and only working on the procrastinated projects in 30 minutes segments which must be followed by enjoyable activities. This is just an example as there are LOTS of good practical tips as well as ideas for getting at the cause of the procrastination problem.
If you are like me in putting off the next action (as well as a million other things in life), you may want to check this one out. Here's the Amazon link: