Chela, I agree with you 100%. Not all businesses work with all forms of social media. You have to consider what type of work you do and your target audience. If your target audience doesn't frequent a type of social media, then you're probably wasting your time there.
In an attempt to find out where (or if) my target audience was on social media, I spent hours and hours during the summer searching the big three--FB, Twitter, and LinkedIn--for all the people I work with now (including my contacts at the larger businesses) and past clients. LinkedIn won, FB second, and Twitter last by a long shot. Most of them I didn't find on any of these three.
And how to get the "right" people to follow you on Twitter for business? Haven't a clue! Except for one to two people, those who follow me are either in the same line of work or connected with me on a personal level.