I think better, more prominent share buttons within Steemit would be great. I'd also like to see Steemit added to services like http://www.addthis.com to generate great follow buttons that point back to Steemit blogs and profiles. I haven't finished my site yet but I've played around with styling a Steemit link to fit with my AddThis buttons, although it lacks their analytic technology. You can see an example in the top of http://www.ithoughtitwouldbezombies.com
I'm a comic artist and could see Steem gaining a lot of traction in the webcomics community. I haven't understood people advertising via billboard, it seems an inefficient use of advertising spend! I've used the advertising service Project Wonderful in the past and think it could be a great advertising channel for Steemit to recruit an artist community. It's heavily used in the webcomic community. I am sure there are other channels I don't know of that are equally catered to specific communities that could be beneficially targeted for marketing. I think we can all work in the communities we are strongest rather than a wide, generalized strategy, and that will benefit Steemit the most.