Here are my five steps to growing a brand on social media. These steps should be re-evaluated every step of the way with a team (or, if you're doing your own branding, by crowd-sourcing your "most important followers" (and yes, that can be your Mom)) to determine how your individual community wants to take your content.
5 Steps to Fool-Proof Growth on Social Media Networks
Content
Decide what your content is (like this blog post, that's a piece of content for my personal brand), decide how you'll get it (write it, pay someone else to write it, or curate it (basically, share a bunch of links YOU like)) and then decide when you'll publish it. I've been using this speech since I spoke at EIJ 12 - "Social Media sharing should be like building a really great ice cream sundae."
The ice cream should be the content that pertains to your brand; for me, it's #glutenfree things, social media news, journalism news and updates on how to survive as a 20-something woman in today's crazy world. The fudge sauce should be personal things; photos of your kids, photos of you "world." Basically, the fudge is a "behind-the-scenes" look at the brand that is You (or the brand itself). Then, add the sprinkles, nuts, cherries and all the other sundae bar items. Those items can be random musings, things you want people to say "hell ya" to or just random links that you find interesting. The toppings are what you give people without expecting any return on investment (ROI). Social Media ROI is INCREDIBLY hard to measure, but basically, if you share this content and grow your followers (even if it's just 1-15 per week), you're earning back ROI on your work.
You should post at least 4-6 times a week. If you're managing a blog or editorial brand, you should post 5-8 times per day.
You should spend 2 hours per day on Twitter. If you're trying to establish yourself as an expert, you should post no less than 5 tweets per day. If you're managing a blog or editorial brand, you should have at least 8 posts per day.
You should post 4-6 times per week. If you're video-focused, make sure you're posting at least one video per week. If you're posting for an individual brand, one video per month is fine, in my honest opinion.
Google+
Ahhh Google+... the community that is basically, an elephant in the room. If you're working on a video project, you need to leverage this. If you want to improve your Google search results, you need to leverage this. Keep your posts to 4-6 times a week if you're doing a personal brand; professional brands should mirror your Facebook/Twitter strategy. If you can run a Hangout, especially a HOA (Hangout-on-Air), you'll gain followers quickly.