Don't flash an immediate smile when you greet someone, as though anyone who walked into your line of sight would be the beneficiary. Instead, look at the other person's face for a second. Pause. Soak in their persona. Then let a big, warm, responsive smile flood over your face and overflow into your eyes. It will engulf the recipient like a warm wave. The split-second delay convinces people your flooding smile is genuine and only for them.