Great organizations have one thing in common: great managers. Much has been written about what makes a great organization, but poor managers can cause even great organizations to lose momentum. So how can successful managers achieve breakthrough performance regardless of the quality of the organizations they manage? From the managers of the Girl Scouts, to Partners In Health, to the city of Providence, R.I., there are four simple management principles that they use to guide organizations from mere mediocrity to stand-out stardom. These four principles -- derived from the recently published book The Breakthrough Imperative in this Stanford Social Innovation Review article -- help make the decisions that lead to breakthrough performance.