Don't Be a Gossip
So you got the memo on being friendly. But, don't let it go to the other extreme. Gossiping is a cardinal workplace no-no, but it's an even more important rule for the boss not to break. Managers are privileged to some heavily confidential information, from their employees' salaries, to the reason the secretary took that week of personal leave, to internal data that could bring the company down. Don't take advantage of that privilege and risk your job or, at a minimum, embarrass your employees.
Beyond sharing restricted info, it's so uncomfortable working at a place where someone is a gossip, especially if it's a boss. I dreaded moments of downtime at my office when my boss was present because he would grill us for the latest news on our dating and relationships. He'd then tattle to the next employee with an open ear. Eventually I stopped sharing stories with even my closest friends at work, because there was too high of a possibility that my boss would get hold of that info. Remember, your employees trust you, otherwise most wouldn't work for you, so honor that trust, and respect their privacy.