I am struggling with this same issue. I have two thoughts: go at it in categories! and, ask yourself if there are emotional/psychological issues making this hard for you.
Firstly, I remember how I used to do it as a kid: first the paper products. Ok, I was a bigger kid by this time :) Anything with paper in it: Kleenexes, papers, magazines, posters, invitations - I would gather them up and deal with them first. Put them away or throw them away.
OK, then I'd look around and see what other categories of things there were - I used to like to categorize. And I'd deal with them. All the toys in their places. All the clothes in their places. All the dishes. Etc. Now I have to add financial papers, work materials, etc etc. More categories. Too many categories now! Ahrgh!
I would also check in with yourself to see if there are psychological issues to address:
Are you subconsciously trying to keep people from interfering in your life/work? A good way to do it is to make sure they can't find anything in your space. :)
Are you putting blocks in your way so you can't go forward? Why? What are you afraid of? Can you let that go?
Do you want privacy and time alone, but you don't want to just say it, so you make it physically impossible for people to come into your space, or make it so you won't let them in due to pride?
Do you feel badly about yourself and fear letting people get too close? If so, again, building walls of clutter will give you a good excuse to keep them away.
Did you grow up with uncertainty or criticism? This can make you feel uncertain or helpless when it comes to organizing your own surroundings.
There are so many other things that can keep us from creating an orderly world around us.