You need to see it as community building. Don't see social signals as "if I put our link on twitter and get people to RT it it will help rankings"
The idea is to put up quality tweets, interact with your followers and give them information on your company, help them when they have problems and build as sustainable and regularly updated twitter account. Create high quality blogs, put them on facebook / google+ and twitter, If you do this right your followers will talk about you, influencers will retweet / like / +1 and this is how social signals work.
It's fair to say at the moment Google pays more attention to their own social network, Google+, but it isn't as popular as the others at the moment.
The summary is just to be active, put good quality content up on your social networks and interact. Your social signals will follow 