Social Media Advertising. What Works Best?

Social Media Advertising. What method works best?  As a businessowner, it's very difficult to choose the best method of "paid" advertising through Social Media.  I've signed on with accounts through Twitter, Facebook, Linkin, Google+ and Active Rain just to name a few.  I've linked some of these accounts together and try to post daily but the time has come to consider "paid advertising."  I thought I was talking to someone from Google the other day, who indicated they could place my business at the top of the search pages (Google, Bing), only to receive an email from this person who was not at all affiliated with Google and after reading several reviews about this particular company, I declined to sign a contract.  It brings me to this question, "What methods works best and who do you trust?"  https://www.facebook.com/ptauctions