Facebook works well for me, got this amazing customer from the US 🙂, and have built a reputation there as a mosaic artist that is useful. Also, I use my work photographs gallery on my professional page there as an easy update of workphotos linked to my website, which means keeping images up to date very easy. The new design I think will serve businesses even better, as it is more website/blog like. BUT, it does make a difference what you're focusing on there, and if you're seen behaving like you wouldn't like to be seen on tilersforums, that is effing and blinding and just going on about negative stuff, well, it would look bad for business, so being positive by and large is a must.
Use twitter and linked in, but have had no business from it, yet, even though it does remind me of some businesses here and there, so I suppose it must work the other way round.