Social media marketing is an art because you have to market to your followers without appearing to be marketing.
Most companies that go in there immediately pitching their products fail because social media is not really a selling platform but a gathering platform where people share useful information.
But, that's just my opinion :-) If you want to watch a couple of webinars that teach how to market on social media use the link below.
There are videos with Rand Fishkin, Mari Smith and Brian Solis. Those are the top names in social media marketing as they have all written books on the subject.
If you want more videos just ask!