Social Networking

I am now on Twitter, Facebook, TechHui, and Blogger. I have no idea what to do with them all. How do I utilize them and for what purpose? Facebook asks "What's on your mind?" Twitter asks "What's happening?" TechHui asks "What brings you here?" Are random thoughts alright? It seems like the way to keep friends and family up to date. I guess I'm still trying to find my voice. What do I want to say?