Thoughtless: Know that self-satisfied guy who unrelentingly decides to hit reply-all to every group e-mail that's sent in your company? You don't want to be that guy on social networks. On Facebook, one of the most utilized features is the Wall. It's a fun place to leave publicly displayed messages and a bit of witty banter. However, making specific plans with a person on the Wall, for example, is rude to that person's other profile visitors. Too many times, you see "let's get a drink at 5 today" posted to someone's Wall. Unless you want to include all of that person's friends in on the social engagement, there's no reason not to pose that question in the private messaging section of Facebook (or any social network for that matter; Twitter, for instance, has the direct message function).

5. Watching Your Tone

Thoughtful: It's important to keep a polite and measured tone on social networks; after all, the mainstream ones like Facebook are an extension of our lives in real life (that's not necessarily the case in virtual worlds, but that's a whole other topic). Say things you'd feel comfortable saying in person, and avoid inside jokes that only a few of your contacts would understand.

Thoughtless: With a social network that is fairly open, nobody is really going to be impressed when you post inside jokes that they don't understand; in fact, you run the risk of insulting people if they think you're making some veiled or coded comment about them. Remember, within most social networks, you can set up private groups where those kinds of exchanges will not only be more appropriate, but also encouraged. "It's better to be clear than clever," Dixson says. "Don't expect people to get it. Be very explicit."

Finally, sarcastic humor and anger can be dangerous in social network postings, just as they are in e-mail messages. Think twice before sharing. (For more e-mail etiquette tips, see Ten Things You Should Never Put in E-Mail.)