1. ALWAYS SELLING

One of the worst sins, says Nika Stewart, owner of social media management company Ghost Tweeting, is posting only when you have something to promote. It’s cheesy and it’s spammy.

Social media is a conversation. No one wants to have a conversation with a door-to-door salesman.

2. SENDING AUTOMATED MESSAGES TO NEW FOLLOWERS

You may think sending a direct message to a new Twitter follower is a great idea, but experts advise to tread lightly.

“Thanking new connections and welcoming them into your community is the right sentiment and can lead to the beginning of terrific relationships,” says Stewart. But auto direct messages on Twitter, she explains, “are generic, and lack any personal information. So in many cases, they make you look uncaring and offend your target.”

3. OVERSHARING

Even if the only connections you have are your 10 closest friends, status updates and tweets are less private than you think. If you’ve forgotten who all your friends are, then definitely save the details of last night’s hookup for a carefully chosen few.

“You should be texting them, rather than posting in a public manner,” says Catherine Cook, cofounder and VP of brand strategy at MeetMe.com. Or better yet, call people one at a time to yak.

4. NOT THANKING PEOPLE

If someone answers a question, or shares your content with an enlightening comment, then acknowledge them. Ignoring them is much like disregarding someone who holds a door for you. It’s bad karma.

5. REPOSTING TOO MUCH

Sending the same link 10 times in two hours may marginally increase the chance people click on your post. But if people stop following you because of your digital clutter, then you don’t come out ahead.

6. SHARING CHAIN LETTERS AND URBAN LEGENDS

Anything that puts unwanted social pressure on people to take action is a bad idea. Likewise, before you share something shocking, do a quick Google search to find out if it’s on Snopes, the urban legends website.

7. VAGUEBOOKING

This is defined as posting a status such as: “I guess I know now who my real friends are.”

“[Vaguebooking] is designed to get the comments,” says Cook. Vaguebooking status updates are “usually something that’s just drama between friends,” she adds. That sort of drama doesn’t win you new Facebook friends or followers.

8. HIJACKING THE BANDWAGON

If you’re interested in contributing to a trending hashtag on Twitter, by all means read and post along. But sometimes people just look at the list and think: “It’s trending! I should use it,” says Cook. “Well, why is it trending? Don’t just hop on.”

You’d hate to post a link to your old travel trips for Rio de Janeiro when it turns out the hashtag has to do with a major natural disaster that just hit the city.

9. LACKING DECORUM

“The broad philosophy is that you should have a bigger filter online than you do in real life, and I think the reverse is actually the case,” says Cook. We say stuff online we’d never tell people to their faces. Even though in most cases, our private nastiness won’t be eternally recorded; whereas our social media posts will.

If you feel the need to insult a whole class of people, swear like a sailor, or post a political screed, ask yourself if you’d do it in front of 100 assembled coworkers, or in front of all your relatives at the Thanksgiving table. If you would, fine. But you probably wouldn’t.

10. BAD ENGLISH

Posting. Periods. After. Every. Word. Or going over the top with ALL CAPS!!!!! On social media–as well as in more traditional communications channels–your choice of language can emphasize a point. You don’t need extra help with punctuation. (Source)