This is a good article about active procrastination. This dated article just provides an introduction but in recent years there been some good books written about this topic.
Much to the relief of those who like to mop up the syllabus just before the semester exams/quiz, pay their bills on the last day or delay a decision to the 11th hour these studies lend support. I move between from being a non procrastinator to an active procrastinator to being a passive procrastinator. When I am actively procrastinating or basically ‘sitting on something’ it may that it is low or high priority on my list but not urgent or that I am waiting for some more information to do the task or take the decision, information or questions which I am not explicitly aware about that is if you ask me what exactly I am looking to find out more I may not be able to say but a hunch tells me to wait for more information or that simply it is not the right time and no need exists to rush. However a busy lifestyle, low levels of overall alertness, not knowing what a person wants or stress can make a person from an active to a passive procrastinator on certain tasks.