How to be a Polite Spectator

A friend and I were recently discussing chess spectator etiquette and how they differ from the arena of Magic The Gathering tournaments.  In Magic tournaments it is considered rude to spectate for a brief period and then leave the table.  Leaving the table can show an opponent that maybe the game is over and any future bluffs shouldn't be respected.  In chess tournaments this happens frequently that when a blunder is made players start to leave the table.  What other forms of chess spectator etiquette stands out as impolite?  What do you find acceptable?

• Walking away immediately after a move
• Facial expressions
• Grunts or snickers
• Walking a few feet away and whispering to another spectator

Please leave your thoughts in the comments below.