Before you start filing, neatly label your hanging folders. My suggested categories are: Taxes, Insurance, Health Care, Banking, Retirement/Brokerage (retirement accounts are many people's brokerage accounts), Credit Cards, Home, Auto, Legal, Estate (for a copy of your will, living will, health-care proxy, and other estate-planning documents), To-Do, To-Be-Paid.
You may also want folders labeled: Pets, Kids, Mom and Dad, Benefits, Flexible Spending, Travel.
Next, label manila file folders to put into each of the hanging folders. Suppose you have three credit cards—MasterCard, Discover Card, and Banana Republic. You'll want a manila folder for each of them labeled with the year: MasterCard 2006, Discover Card 2006, Banana Republic 2006. When the year turns to 2007, you will make new manila folders labeled "MasterCard 2007," "Discover Card 2007," and so on. Once you pay your taxes and close your personal books on 2006, you can take all the 2006 folders out of your box and move them to a file drawer in which you have hanging folders set up in a similar way. That way your bills-in-a-box filing system remains portable, and you will be able to put your fingers on any important piece of paper at any particular point in time.
You'll eventually get good at figuring out what category needs its own folder. Give yourself leeway to create the folders you think you will need.
And that's it. Now you're set to start organizing using the Four Ds.
Next: What are the 4 D's?