The “Under 10 Minutes Rule” is simple. It states that if a task arrives in your queue and it can be completed in less than 10 minutes, you take care of it right away.
Why does this work? Well, first of all, you are more likely to procrastinate on smaller tasks, allowing them to become bigger and bigger over the course of the day as more time and thought are put in than necessary. Secondly, you are more likely to get results when a task is finished immediately. Small assignments are the most vulnerable to being buried in the workflow and never attended to. You say “I can do that later,” but “later” never arrives.
Of course, the “Under 10 Minutes Rule” is only effective if you leave some wiggle room in your schedule. If you have back-to-back meetings or multiple assignments that require heavy lifting every day, you just won’t have time for anything else. Therefore, you should assume that you’ll spend at least an hour per work day dealing with these small tasks and budget accordingly.
In my mailbox, as soon as a task has been attended to, the corresponding messages are removed and placed in an appropriate folder. Thanks to the “Under 10 Minutes” Rule, my inbox is nearly always empty. I don’t lose things due to clutter, I don’t get overwhelmed by all of the things I have to do, and my level of responsiveness is second to none.
To crystallize how this works in practice, here are my to-dos for a given work day. At the bottom are “Under 10 Minutes” tasks that came in that day, and went right back out.
For an example of theory in practice, see the full post at Intuit's Fast Track blog.