Jennifer Aaker, a Stanford professor, and Naomi Bagdonas, an executive coach, say that, even in times of stress and crisis, leaders should use and encourage good humor and levity at work as a way of building employee morale and engagement. That doesn't mean you have to tell jokes all the time. Instead, figure out what kind of humor works best for you and learn to pinpoint the opportunities for using it to best effect. They explain what makes things funny (hint: surprise) and the pitfalls managers should avoid. Aaker and Bagdonas are the authors of the book “Humor, Seriously: Why Humor is a Secret Weapon in Business and Life.”