On a recent visit to Duke University, Apple CEO Tim Cook was asked by a student, "When should we listen to our professors and when is it OK to break the rules?"

Cook smiled. "You should rarely follow the rules," he replied. "I think you should write the rules.

"I think if you do follow things in a formulaic manner, you will wind up, at best, being the same as everybody else."

When companies follow the rules, he continued, they are successful for a little while, but ultimately they won't succeed.

That said, Cook doesn't dismiss formal training. What Duke's Fuqua School taught him so well is how to learn, collaborate, and work with people who have different perspectives.

"To me, that was the overwhelming value of being here--not the specific rules of marketing or strategy or operations," Cook said.