I have found a very useful article about social media and companies in a Spanish magazine. This article explains what are the mistakes that you shouldn’t do as a community manager in a company:

1. Making posts only about your Brand: the social media is not an online magazine about your products. You must write interesting articles that may be useful for other people. Of course you can introduce new products and news about your brand but always with an interesting article behind.
2. To include not descriptive links: when you include a link in your post you have to make sure that people will click in the link, so you must write a post which drive people to click the link.
3. Delete the negative comments: It is true that the critics of people can underestimate your Brand, but it is also true that gives credibility to your profile. The critics are also an opportunity, as you can respond them and create engagement with the users.
4. Not responding to your fans or followersà To create engagement you need to have a social network with fluent communication. If your fans ask questions or make some suggestions you must answer them.
5. Not thanking your fans and followers: Saying thank you to your fans and being nice to them will increase their loyalty towards your Brand.
6. Making understandable posts à People will reject your Facebook page or twitter if they don’t understand you.
7. Not keeping updated your social network: Social media is the most immediate way to have new information, so your social network has to be always updated, if not people will unlike your pages.
8. Abusing hashtags: Twitter is a good media to summarize information of your Brand and hashtags help you to classify this information better. But be careful with adding a lot of hashtags in one tweet.
9. Not following your competitors: it is good to follow your competitors to see which are the best practices.
10. Being in only two social networks: It is positive to have more tan two social networks for your Brand as you will be able to reach a bigger audience.

I think this advises could be very useful. Every time more there are more people connected to these social networks and companies should now how to communicate through them.