"If someone wants to see him," [Jason] Fried writes of Buffett, "they are told to call and set up the meeting when they can see him tomorrow. So if you want to meet with him next Friday, you call next Thursday and say 'Can I see Mr. Buffett tomorrow?'"
Why is this a good idea? For Fried, the beauty of the approach is that it puts Buffett back in the driver's seat, allowing him to control his schedule, rather than the other way around. This way, if something comes up (and when does something not come up?), Buffett is free to react instead of being hemmed in by pre-commitments.
[Execupundit note: I share some of the skepticism. It's much easier to set such a rule when you are Warren Buffett but it is an approach to keep in mind if only for occasional use.]