A charming person is one who makes others feel witty, smart, beautiful, etc. So, if you are hoping to charm somebody: Smile. Open doors. Ask questions about his or her interests or areas of expertise. Evince genuine interest in the answers. Be creative in doing kindnesses without being asked -- bring a drink or a treat, discover a preference, etc.
In other words, charm is all about how you make the other person feel -- not about your own performance. If you cannot resist telling what you perceive to be charming stories or jokes, make them low-key, self-deprecating, and extremely short.