Only post advertisements for your business. Don't put personal shit on the internet.
I know a self-employed gal (belly dancer / teacher) who uses facebook very well as a way to get gigs and keep her classes full. It's about her, of course, but she uses it more like a big-shot CEO uses twitter - promotion and influencing - than as a view on her personal life - she doesn't even list her kid or hubby on relations, nor does she share pictures of them.
That's the right way to use it - it's all potentially public to everyone, but she gets a revenue boost by using it so it's a win/win for her.