Social media marketing is about building a community and engaging that community based on the community norms and goals
Do's
Define a target segment (the characteristics of the community you want to build)
Define a theme (the community should be addressing topics, discussions, news, fun, all around the defined theme)
Do regularly update quality content, respond to comments, queries and complaints
Add value to the community by contributing something worth while
Do measure, analyze and respond to insights and stats
Do not's
Don't try to sell to your community, at least not directly
Don't focus on getting more engagement matrices without meaning to the purpose. By which I mean, don't try to get more likes, shares, retweets by posting cute baby pics or puppy photos which has nothing to do with your brand
Do not engage in a heated discussion, or even worse, an argument, within the community platform
Don't try to grab attention by cheesy tag lines without proper content