Imagine yourself in this position: Less than five months ago, you were summoned from the private sector to join a newly formed national government. Your background is in retail; now you are heading up the nation’s mining industry. You are abroad on a state visit, still working to come up to speed, when word reaches you from your home office that there has been a mining disaster—a cave-in deep below, death toll unknown, nearly three dozen missing.

Or envision this: For decades, your financial services firm has sailed along. Not only have revenues soared, your company has also earned a treasured AAA credit rating while creating an extraordinary wealth engine: a little giant of a division that insures against debt defaults, including subprime mortgages. Continuing prosperity seems predictable, but suddenly the market implodes. Subprime mortgages turn noxious. Lehman Brothers goes under. Your AAA rating slips to AA, then A-. With the downgrades, you have to post billions of dollars in collateral that you simply do not have. This boat is sailing straight toward a roaring waterfall, and you are standing at the helm.

Or this one: The enemy has surrendered after a four-year conflict that has left more than half a million dead, and your army commander has assigned you to arrange one of the war’s crowning moments, the formal surrender of the enemy’s most venerated army. The tone, the texture of the ceremony, the formalities of receiving the enemy–they are entirely for you to craft.

These are not, of course, hypothetical or anonymous events. Laurence Golborne, the new mining minister for the Republic of Chile, was visiting in Ecuador on the night of August 5, 2010, when his chief of staff back in Santiago sent him a simple but urgent text message: “Mine cave-in Copiapó; 33 victims.” Twenty-eight hours later, at 3:30 a.m. on August 7, Golborne arrived at the remote site of the mining disaster in the Atacama desert of of the mining disaster in the Atacama desert of northern Chile.

Soon, hundreds of millions of people around the globe would be witnessing one of the greatest mining rescues of all time.

Like the miners in Chile, American International Group (AIG)—the financial services giant heading for the cataract—was ultimately rescued through direct government intervention. The company was deemed “too big to fail,” though it proved almost too toxic to save. When the subprime mortgage market in which AIG was deeply invested began to collapse, top AIG executives had taken few defensive measures. Their tonedeaf response to the tumultuous events that unfolded left the company vulnerable to one of the greatest corporate collapses in business history.

How different the actions taken by Union officer Joshua Lawrence Chamberlain when General Ulysses S. Grant handed him the historic duty of arranging a follow-up ceremony to Confederate General Robert E. Lee’s surrender of his army at Appomattox. Instead of humiliating the Confederate force, as might have been expected after four years of civil war, Chamberlain ordered a respectful alute and launched a healing process to help reunite a country.

Two of the leaders we have just met were well prepared when summoned to moments of decision. Others, recent history showed us, were obviously not. To be sure, few of us are likely to have our mettle tested in such trying circumstances. But all of us can and should prepare for less-public crises in our own spheres of serving, to be ready to act when it really counts.

That preparation comes down to mastery of a limited set of leadership principles. From development work with hundreds of managers and executives in leadership programs in Asia, Europe, North America, and South America; from research interviews with managers in the United States and abroad; and from witnessing managers facing a range of testing moments, I have concluded that their experiences for better or worse point to a core of mission-critical leadership principles—a Leader’s Checklist—that varies surprisingly little among companies or countries.

I have also become convinced that with leadership, as with much else, brevity is the soul of wit. Albert Einstein once described the calling of modern physics as an effort to make the physical universe as simple as possible—but not simpler. The Leader’s Checklist is likewise at its best when it is as bare-bones as possible—but not more so.

Would you have surgery performed by a doctor who routinely failed to confirm that the right patient was in the operating room and the correct procedure was about to be performed? Or willingly fly with a pilot who regularly failed to check wind speed, flight plan, and all the other essential ingredients for ensuring a successful takeoff? Obviously not, and yet those in leadership positions often fail to require the same of themselves.

Through the simple step of creating and consistently applying the equivalent of a pilot or surgeon’s checklist, a leader is better prepared for whatever lies ahead. The absence of a complete checklist is one of the most serious but also most correctable lapses in leadership. And just fifteen mission-critical principles define its core for most leaders. Together they provide an action map for most leaders, in most endeavors, in most situations—whether retrieving mineworkers, saving a company, or reuniting a country.

Adapted from The Leader’s Checklist by Michael Useem (© 2011), published by the Wharton Digital Press. Available through ebook retailers including Amazon, Barnes&Noble.com, and Apple iBookstore.