Keith tells the story of giving an intern the task of getting smoothies delivered to the office at 9pm to reward Square's engineering team—a task that had stumped multiple people. Once the intern solved it, he gave them something more important and consequential to do.

"There will be some people who you don't expect—with different backgrounds, without a lot of experience—who can just handle enormously complicated tasks. So keep testing that and pushing the envelope."

Everybody has some level of complexity they can handle. The job of a manager is to keep expanding scope until you find that breaking point—then park them just below it.

Watch who people walk over to for help. If coworkers keep showing up at someone's desk, that person is a force multiplier—promote them and load them up with responsibility as fast as you can.