These are mandatory in-game and in the official IRC channels and the forum.

IRC etiquitte and in-game

using the '/me' command on IRC

/me kneels to your liege
/me Bows to someone of your rank (if your the one approaching them)

/me rise the liege tells the person kneeling to rise
/me sit down when in meetings the host (Most likely me) will tell the people attending to sit
/me stand up the same above but standing up instead
/me stands to attention when your a soldier of any type and your in the presence of a superior you'll be to attention
/me at ease a superior can make the soldier at ease
/me silence a Liege can demand lowers to stop typing/talking
/me applause

Forum Etiquette

The calling etiquette of the leadership is as follows

If your in the presence of one liege you just say 'sir' to him/her

A Huscarl/Knight

Simply Sir


Baron/Chief (Barons are in control of forts, Chiefs in control of villages)

A Baron, so I would call Stigwig Baron Stigwig

Count/Karl

Count/Karl xxx.

Duke/Lord/Jarl

My Lord/Duke/Jarl

King

My liege, your grace, your majesty.