Beware of the impractical idealist. Idealistic people who have moralistic notions about how people should behave without understanding how people really do behave do more harm than good. As a global macroeconomist and businessman and as a philanthropist I have seen this repeatedly in all those domains. I have come to believe that as well-intentioned as they are, impractical idealists are dangerous and destructive, whereas practical idealists make the world a better place. To be practical one needs to be a realist—to know where people’s interests lie and how to design machines that produce results, as well as metrics that measure those benefits in relation to the costs. Without such measures, waste will limit or erase the benefits, and with them the benefits will keep flowing.

Don’t assume that a person who has been successful elsewhere will be successful in the job you’re giving them. No matter how good you are at hiring, some of your hires won’t work out. Know how the people you’re considering operate and visualize how that will produce successful results. Knowing what they did is valuable only insofar as it helps you figure out what they are like.
