I'm the lazy type that posts my art all the places. I can't figure out the logistics of having different things different places, I just end up confusing myself.
What I usually do is submit my art to DeviantArt and then link to it on my Twitter with a low resolution version, and also throw the link on my facebook.
Generally I have a feeling different people follow me different places. Facebook is mostly family and irl friends, while twitter mainly are people from the webcomic community, and... well a bit of everything on dA. There's a bit of overlap there...
Sometimes I also just take some pictures of wips on my phone and put them on Twitter, just because that's convienient.