I think it's also important to remember the "social" part of social media advertising, i.e. the people-to-people part. Of course, it's very important to be choosy about what you post on social networks to promote your image, but in my opinion it's also a good place to sound more personable with your clients/customers. Sound genuine, not too gimmicky. People like feeling like they're buying from a real person and not a faceless entity like a 'company.'
Keeping updated company profiles on Facebook, etc., and posting regular Tweets to keep your customers up to date and engaged lets people see that you're open and trustworthy. It also lets them interact with whatever you post by liking or sharing it so you can potentially get a lot more (free!) exposure if a lot of people share your tweet/post.