What social networking site brings in the most work

Why do you say that? There are so many out there, it would be great to know why you think that

For me it is linkedin but this is due to the nature and industry of our business, I guess it changes for everyone

Aside from liking other business facebook pages, and follow some business twitter accounts, you must also be communicative with them. Well, I've liked/followed some websites, and they followed/liked back.. But if we can communicate with them by commenting on their post that we found interesting, other websites will see us and hopefully befriend or get in touch with us. ;D

Social media is a great way of increasing your regular readership and getting people to come back and visit you over and over, but you still need a selling strategy and content or pre-order pages to point all that traffic to.

People aren't as likely to buy something off their own backs unless you put it right in front of them.

In my opinion, Pinterest is a great platform for getting more traffic. Pin the images present in the blog posts and you will get the best of benefits.