I'm still in an info-gathering/digesting phase, but I can say a few brief things about social media strategies:
1. Check out the summary and SIG from last year, of course.
2. I would think carefully about what your overall and specific goals are for social media. Is it simply to share your 3D work with as many people as possible? If so, which people: 3D fans, or people interested in 3D, or laypeople? Or is your goal to recruit people for a 3D group or event? If so, is your immediate goal to direct them to your website, to register? Or to sign up on a email list? Or is your goal to bring more people into the 3D fold (convert them to 3D, one might say, haha)? Your answers will determine things like the best platforms and the best 3D formats for you, whether you need a website, etc.
3. Building a presence/following works differently on every social media platform. But regular activity is a must for most of them, as is finding out where and when you can engage with the most people. In some cases, like FB, the answer to the latter might not necessarily be to focus exclusively on creating new pages/groups, but to do that in conjunction with joining and engaging with already established communities.