LinkedIn, Twitter, and Google+.
This is what you need to do to maximize your presence at those sites and minimize the amount of time that you waste on them.
By far the most important place to establish and continue your professional reputation is LinkedIn. If aren't there, you are invisible. Filling out the profile is like filling out an application for a job interview, so expect it to take some time. Be specific about places, dates, people. Linkedin is a serious place for grownups, it's not about LOLHEHEHE, it's about making business connections. Think of it as a casual business group meeting. There is no need to walk in wearing a top hat and tails, but it's also no place for being silly. Make connections, drop names. If you worked with me in the '90s, say so.
This is critically important for exposure. And the good news is that you can link your posts from LinkedIn to be posted automatically on Twitter. I wish that you could do that with Google+, but as of this writing, you can't. And while posting automatically is a timesaver, it doesn't mean that you should never visit your Twitter page. Go look at it every once in a while.
And by the way, don't "tweet". Your customers don't care that you are in a restaurant enjoying a sandwich right now.
Be sure to complete your Google Profile, which is what everyone who searches for you finds in Google. The good news is that it's the same one that you are already using for your Google Blog (if you have one) and Google+. If you filled it out quickly a while ago, go back and check it, update it if necessary. If you have a Google+ account, and have no posts, or only one post, or if the last post is from months ago, you look like you went out of business. You may not be paying attention to it, but other people are.
By the way, don't feel obliged to post goofy, useless things like #crocidileteethtuesday, which has become popular there. Post interesting, short posts about your business and always include a photo.
And that's it. If you're wondering why I didn't mention Facebook, or Tumblr, or any of the thousands of other social media sites, it's because they a waste of time for business. If you would like to catch up on what's going on with your cousins, or share cheat codes with other gamers, or if you just like what I call *monkey chatter*, please enjoy them. Someone will *like* your post, and if you're really lucky, someone will write *LOLHEHEHE*
But for business, stick to the big 3.