1. Don't answer a telephone call with an e-mail.
Or an e-mail with a text message. Or a text with a Facebook message. In the communication hierarchy, you generally want to match the level of intimacy or move up the hierarchy—a move down can look like you're avoiding the person.
2. Do ask before you post pictures from a party...
...whether anyone minds having them on Facebook. If someone is social-media-shy, save any photos of her for your non-Facebook albums.
3. Don't text at the movie theater...
...no matter how strong the urge to LOL. If you're perpetually rattled by the glowing phone screens of others texting during movies, do bring a tiny penlight to shine on them. It's more discreet than shushing but still delivers a wallop of social shame.
4. Do embrace the 2.0 version of thank-you notes.
Text or e-mail a digital snapshot of you enjoying the present to the gift giver. Because nothing says thank you like photographic evidence.
5. Don't respond to a long, thoughtful e-mail merely with "Thx."
"Thx" will not make people look kindly on you—in their eyes you'll always be more Charlie Sheen than Tom Hx.
Next: How to solve your toughest Facebook dilemmas