Do tips make for better service?

DAVID FRANK started working for tips when he was 11 years old, delighting restaurant diners in New York with his magic tricks. As a teenager he would make an average of $60-70 in an evening—not bad, but he wanted more. So he started reading research on tipping, and found a study showing that servers who left a sweet at the end of the meal could up their pay. He tried handing punters a playing card at the end of his act, hoping that the memento would persuade them to part with more cash. It worked.