So this is interesting because you are coming at this from a very different perspective than most people who are interested in productivity (and you're a bit closer to my own way of doing things)
So when I was first trying to manage my todo list I had a pen and paper notebook - tasks got crossed out in pen and new ones were added at the bottom. You read from top to bottom so that oldest unread task was the first you saw - once you had done everything on a page you could tear the page out. Now, with this approach the 'gain in priority' is inbuild - tasks you have been avoiding become more and more obvious as time goes on.
This approach is actually continued in my current system (I use my inbox for tasks and send myself a lot of mails). Each day I make it a rule to tackle my oldest task.
But we should contrast this with the normal way of thinking about productivity, which is that it's about doing what's important, not what's urgent. I think Randy Pauses explenation is the best so I'm going to ask you to watch from 20:30 of this video http://www.youtube.com/watch?v=oTugjssqOT0
(transcript below)
This is the most important slide in the entire talk. Due Soon Not Due
Soon Important Not Important If you want to leave after this slide, I
will not be offended, because it's all downhill from here. This is
blatantly stolen, this is Steven Covey's great contribution to the
world, he talks about it in the Seven Habits book. Imagine your To Do
list - most people sort their To Do list either "the order that I've
got it", throw it at the bottom, or they sort it in due-date list,
which is more sophisticated and more helpful but still very, very
wrong. Looking at the four- quadrant To Do list, if you've got a
quadrant where things are "Important and Due Soon", "Important and
Not Due Soon", "Not Important and Due Soon" and "Not Important and
Not Due Soon", which of these four quadrants do you think, upper left,
upper right, lower left, lower right, which one do you think you
should work on immediately? Upper left! You are such a great crowd.
Okay. And which one do you think you should probably do last? Lower
right. And that's easy. That's obviously number one, that's obviously
number four. But this is where everybody in my experience gets it
wrong. What we do now is we say: "I do the number ones, and I move on
to the stuff that's "Due Soon and Not Important". When you write it in
this quadrant list, it's really stunning, because I've actually seen
people do this and they say: "Okay, this is due soon and I know it's
not important so I'm going to get right to work on it." The most
crucial thing I can teach you about time management is, when you're
done picking off the "Important and Due Soon", that's when you go
here. Due Soon Not Due Soon Important 1 2 Not Important 3 4 You go
to "Not Due Soon and Important", and there will be a moment in your
life where you say, "Hey, this thing that's due soon and not
important: I won't do it! Because it's not important! It says so right
here on the chart!" And magically, you have time to work on the thing
that is not due soon but is important so that next week it never got
a chance to get here because you killed it in the crib. My wife won't
like that metaphor! But you solve the problem of something that's due
next week when you're not under time stress because it's not due
tomorrow. And suddenly you become one of these Zen-like people who
would just always seem like they have all the time in the world
because they figured this out.