I've been on Twitter, Facebook, Google+, Linkdin, etc for a few years now and have tried many approaches to creating and using engaging content. I've had some big successes and some massive failures, but to date the information that I've come to think of as invaluable hasn't changed much. A few tips from an experienced doer of stuff.
1. Ask yourself if someone who doesn't know you would respond to your tweet or post differently than someone who does.
Often the best posts in your mind will leave others wondering what the hell you are talking about.