http://www.bitrebels.com/social/social-media-for-business-guide/
"This is no different than talking to people in different real-life situations. The same commonsense and polite behavior applies [...] Navigating social media was just another chance to form bonds with people by being respectful, helpful, engaging and authentic." - Modern Etiquette: Social Media Do's & Don'ts
1) Whatever you say on social media is in public and is permanent. Even if you delete a tweet or comment later, the damage is done.
2) Don't overshare or put out too much personal information. You don't need to update the world every second. Don't share things that aren't relevant or appropriate. Consider creating multiple social media accounts for your different passions.
3) Don't beg for attention. Don't ask for more likes, don't like your own posts. Stay professional.
4) Be aware of your tone. Try not to vent, brag, complain.
5) Don’t Respond to “Haters." Feel free to block the offender. Stay out of any argument on social media.
6) Post only what you have permission to post. Ask before you tag people in your photos. Credit work that is not your own.
7) Own up to mistakes. #CommaFail
See: Social Media Etiquette Allows No Vaguebooking, Oversharing, Overposting or Duck Faces
The Marketer's Guide to Proper Social Media Etiquette