A simple 3 x 5 card with this management principle written on it explains the disappearance of Lehman Brothers and Bear Stearns, and the economic havoc wreaked by Bernie Madoff.

Another rule that is worth adopting in today's new managerial curriculum is #50: On your way up, pay attention to your strengths; they'll be your weaknesses on the way down. Venture capitalist John Doerr of Kleiner Perkins taught me this rule. It's too bad the top executives at General Motors, Ford, and Chrysler weren't there with their own 3 x 5 cards when John said it. For years the mantra in Detroit was, "Big cars make big profits; small cars make small profits." As it turns out, big cars also leave big craters when the game suddenly changes. It's not just that what goes up must come down. It's more that what took your company (or career) up is more than likely to be the very thing that brings it back down. Learn to pay attention to your strengths and your weaknesses; depending on the circumstances you find yourself in, they can be the same thing.

The ultimate lesson of the 3 x 5 card school of management is this: in turbulent, unpredictable, rapidly changing times, we're all looking for things that work. The old rules don't fit the new environment. They either don't produce the right results or they simply don't adequately describe what we see unfolding in front of us. As managers and leaders, we all need to look with fresh eyes and listen with open ears; we need to come up with our own rules of thumb, ideas and practices that help us make sense of change as we make our way in the world. It could be as simple--and as insightful--as a collection of 3 x 5 cards.