Sound advice. It is one of those things that no one will ever look at unless I get laid off or die.
I wish this were a joke... But you should follow the WOTR system of filing. There needs to be one pile on your desk of "must get done, they will never be forgotten" project papers. And then two or three other piles scattered around the office. (Mine presently reside on the corner of my desk, my bookshelf, and the window ledge.) Whenever you have something cross your desk, you determine if it needs to be in the "must do" pile. If not, you randomly place it in one of the other stack of papers.
There need not be any rhyme or reason behind your decision of which of the "less important" piles the paper lands in. Consult the magic 8 ball if you think it will help. Anyhow, every few months- when a pile grows too large, go through it. Lots of the papers near the top will still appear to have some possible importance and become the bottom of the new pile that you start in a new location. As you work your way to the bottom, you are likely to find that most, if not all of the papers can be recycled and they were not nearly as important as you thought at the time.
It is only on a rare occasion that you realize you did not categorize the paper correctly initially, and it needs immediate attention. Then it is either placed on your computer keyboard, or the top of the "must do" pile (depending on how close to the deadline or past the deadline it is.)
Again, I wish I were joking. But you would be amazed at how much time each year this method saves...