I mirror my comic pages on dA, plus post original art there. Facebook and Tumblr update less frequently, mostly finished art and comic updates, though I am considering doing more general comic/art-related blogging. Can't decide if I wanna put that on Tumblr or go back to dreamwidth/wait for pillowfort.io
I'm most active on Twitter, which is about 70% comics and art talk and 30% politics.
I have loads of social media up my sleeves: I use Facebook and Twitter for comic and video (and occasional website) updates. There's YouTube, where comic related timelapse videos go, usually coverpages and illustrations, but there is a video showing a non-coverpage too. Most of the illustrations and coverpages are showcased on Pinterest and Deviantart plus on Instagram as well. Instagram is fully managed by Liz, and there are occasionally WIP images too here.
I use pretty much all I can, but it's all centered on my wordpress install (tfti.inkorpora.com) because it is the most flexible. So I have two main paths:
From Wordpress, I post to twitter (@inkorporate), Facebook (http//facebook.com/inkorpora.comics), Tumblr, pinterest & google +.
From my instagram (@ink_orporate) I post to wordpress, Facebook and twitter. I use instagram for sketches. Quick tip: If you want instagram images in your twitter post (you should), you can use IFTT.
I also post pages to deviantart from time to time (ink-orporate.deviantart.com)
I seem to be gaining followers mostly on Instagram & Twitter. I still have a bit more on Facebook, but it's growing more slowly.
Tumblr, pinterest and google + don't give me much but the wordpress plugin works automatically so no work on my part.
I'm @StevenLPotts on Twitter, though I've been more active on the comic's Twitter as of late @CowansCrux as I'm trying to build its follower-base. On Facebook the comic can be found at https://www.facebook.com/cowanscrux