Know how valuable your time is. As Bill Gates has written, “No matter how much money you have, you can’t buy more time. There are only 24 hours in everyone’s day. Warren has a keen sense of this. He doesn’t let his calendar get filled up with useless meetings. On the other hand, he’s very generous with his time for the people he trusts. He gives his close advisers at Berkshire his phone number, and they can just call him up and he’ll answer the phone.”