When your desk is a mound of paper that spills over onto every available surface, including the floor, it's natural to feel that you just have to buckle down and start sorting it from the beginning. But if you do that, you never get ahead.
It's better to start handling the paper that comes in every day; mail, flyers, newspapers, receipts, etc. Each day, make time to open and sort your mail, make decisions and route the paper where it needs to go if you can't act on it right away. Spend a few weeks making this a habit.
Once you master the daily paper, you'll be able to start working more effectively on the backlog with your new skills.
Stack of stones from Demion's photostream.