My favorites are "Offer your seat to... people with fire arms" and "Put your napkins on your lap-and leave other people's laps alone."
No one teaches etiquette any more, do they? While growing up I was always taught to put a napkin on my lap while eating, especially at a nice restaurant. No one else does that any more. You should say thank you, push in your chair after you leave a table, have a general respect for others, etc. Etiquette, manners, they are quickly becoming lost art forms.
I can picture our great great grandmothers, were they in our position, telling their children to sit up straight, not to use slang, and to put that cell phone away.
Do you still teach your kids etiquette? Did your parents teach you?