In my planner, on my important numbers list, I have a column called reference numbers next to the company's telephone number.
When I phone the insurance company, I don't have to bring my whole Household File to the phone because my policy number is right there on the form. Or if I phone the water and electricity department to query my account, my account number is readily available.
This saves a ton of time, not to mention the convenience of not having to have all that paper around adding to the clutter!
What good ideas can you add to the discussion?