After years of trying different task management approaches, I have settled on one golden rule: keep them all in one place. I don't actually think the system matters that much, or the software; as long as all of your tasks are in one reliable place that you check regularly, you are safe.
Why is this so important? It's back to visibility again. Things can be in plain sight and yet you can still be blind to them. I'm sure we've all got desks with tasks in lots of different locations: some left in your email inbox, some on post-it notes or scraps of paper, some in the 'tasks' section of your email/calendar program and some in your head. All of these locations might be right in front of you, but if you have to divide your attention between multiple locations they can quickly become invisible. They magically slip out of consciousness and might as well not be there at all. At best, you might be reminded of them at the end of the day as you start to close your open programs - but maybe not even then. I find scraps of paper are most vulnerable to this visible but invisible syndrome. If your desk is cluttered with papers, they quickly fall out of conscious attention and they might as well not be there at all.
Also, having your tasks in one location let's you take advantage of another useful human attribute: habit formation. If you constantly check one place, the habit of looking there builds up quickly and make the tasks in that location visible.
This approach is worth considering elsewhere - are there other areas of your work where you divide work products into multiple locations and formats, making them effectively invisible though in plain sight? More on this later me thinks....
