We use a content calendar that you can plan a week ahead and it could look like this
http://imgur.com/6YtBw73.
In addition I suggest using a tool like Buffer (free to a certain degree) to schedule posts ahead. That way you only have to interact with fans since the posting is automated.
As main social platforms we concentrate on Twitter, Instagram, Facebook and Tumblr. Reddit is another good but tougher to reach.
Another thing I suggest is creating lists on Twitter to keep track and stay in touch with certain people & fans, we for example have:
1. Most Active Followers
2. Top Gamedev News
3. List of Top Influencers
4. Industry Leaders
5. Competitor List
Nurture them over time (the most important ones are Top Influencers and Most Active Followers to us)
I suggest making most of them private.
Your overall goal should be to drive people to a certain action (Call to Action). This could be a link for a newsletter sign up or a new blog post you created. Track every tweet and post and test what worked and what didn't - adapt if need be.
Hope that helped a little