Americans sit through some 11 million meetings every day — with the unproductive ones costing companies $37 billion a year. We’ve already learned that meetings fall apart thanks to sloppy agendas, un-articulated ground rules, and other structural mistakes. So we decided to look at how some of the most effective executives in history — from GM czar Alfred Sloan to Apple prince Steve Jobs to Facebook queen Sheryl Sandberg — run the meetings that invariably fill their calendars. Here’s what we found.