"At his peak, Joe Girard sold more cars per day than any other car saleman in America, according to the Guiness Book of World Records.  In fact, there were some months when he sold almost twice as many cars as his closest competitor.  Girard is not shy about sharing his secret: Greeting Cards.  Every month, every person who had ever bought a car from him got a greeting card.  Christmas, Valentine's Day, St. Patrick's Day, a birthday whatever.  Girard became a member of the family, so to speak, That's a critical secret making sales".
~Jay Levinson, Home Office Computing, April, 1994.