Your teen probably has a cell phone and is likely an avid texter, so this is a good place to start your tech etiquette talk. Teach him or her that when you're in a public place, stepping outside to take a phone call is usually a good idea. If you're in the grocery store and you have to exchange some quick information, that's generally considered OK, but chatting away about anything and everything in smaller, more confined places is rude. We're talking restaurants, small shops, bookstores, elevators and any other place where everyone else can easily hear your conversation.
When it comes to texting, it's a quiet affair so you can get away with it in close quarters. But teach your teens that the phone should go in your pocket when you're engaged in a conversation with someone. Nothing can make a person feel insignificant like staring at the top of someone else's head while he or she is buried in a cell phone. A good rule of thumb to follow is if you wouldn't pull out a crossword puzzle and do it in front of someone, don't pull out your phone. Teach your teen patience, and that the text or e-mail can wait. And if it can't wait, then teach him or her that it's OK to politely excuse yourself to deal with anything that needs your immediate attention.
As for e-mail, it's important to teach your kids the etiquette of sending out links. The rule of thumb here is to never send more than two links to anyone in any given day no matter how cute the kitten in the link is. Another key for sending links is to know your audience. Teach your kids to be respectful of other points of view, and not to send controversial links to simply stir the pot. If your teen is sending out information he or she believes to be important, make sure he or she understands the concept of fact checking the link first.