By the age of 16 (and presumably as an exercise in penmanship), George Washington had copied by hand the 110 Rules of Civility and Decent Behavior in Company and Conversation, based on a set of Jesuit rules in the 16th century.
Today, many of these rules now seem quaint, but their gist should remain relevant (indeed, I'm sure many of us need a refresher in civil behaviors!) For example:
2nd. When in Company, put not your Hands to any Part of the Body, not usually Discovered.
4th. In the Presence of Others Sing not to yourself with a humming Noise, nor Drum with your Fingers or Feet.
13th. Kill no Vermin as Fleas, lice ticks &c in the Sight of Others, if you See any filth or thick Spittle put your foot Dexterously upon it if it be upon the Cloths of your Companions, Put it off privately, and if it be upon your own Cloths return Thanks to him who puts it off.
89th. Speak not Evil of the absent for it is unjust.
You get the picture. Link