This is not an exhaustive list. It was inspired by a quick look at a company profile on Google +. I used to follow that company but just stopped because it clearly is not paying attention to its own posts. It was guilty of all 3 of these:
1. You only post self-promotion and nothing else.
2. You don't respond to any of the comments on your posts, including those with direct questions.
3. You have one guy post "Thanks a lot, [profile name]" on each post, which just makes it look like you hired someone not very bright to comment.
In other words, #DoingItWrong
If you have any other signs of doing social media wrong, please write them in the comments!