From the time we learn to speak, we're told that if you don't have anything nice to say, don't say anything at all. When you become a manager, it's your job to say it—and your obligation.

Author Kim Scott was an executive at Google and then Apple, where she worked with a team to develop a class on how to be a good boss. What emerged was her vital new approach to effective management, Radical Candor.

Radical Candor is a simple idea: to be a good boss, you have to Care Personally at the same time that you Challenge Directly. When you challenge without caring it's obnoxious aggression; when you care without challenging it's ruinous empathy. When you do neither it's...