Sometimes it's better to devote a couple of hours a day to the job until you're done. Have on hand a trash can, a pen, file folders, labels and the other desk organizational aids mentioned above that suit your needs. Then make a big pile of all the paper. Even when you are feeling overwhelmed, just keep sorting and categorizing. If you devote the necessary time, your desk can be cleared.
Organization is a skill that can be learned.
The key to getting better organized is to start with one small step and then take others one at a time. You may find that what you've put off for years takes only an hour to do. And once you see the benefits in one part of your life, you'll be motivated to go on. If you implement the ideas given here, you'll be free from chaos and feel in charge of your life. Once you've started, stick with it.