Ahhh the joys of social media, you can vent, you can keep in contact, you can advertise, and you can well...destroy your career. Don't want that now do you? I'll be honest with you. I hate social media, it sucks my time away, but it is honestly the only thing that has worked for me as far as building my platform and my marketing. Now you're wondering where this comes into play when it becomes to being professional. Imagine you're a reader and you're talking to an author, just in passing, an elevator or something and the first thing he/she says to you is. "Oh my fucking god, someone gave me a one star review! How dare they not appreciate my genius!"
Now I hope realize that it's rude and probably should have been kept in the authors mind. I get being frustrated, especially with drive by ratings, and reviews that just make no sense to you. I get it, I do, but here's the deal. They are going to happen. Every author gets bad reviews. Don't believe me? Go look up your favorite authors. Honestly, as a reader, I don't trust a book that doesn't have at least one low rating. Why? Because I feel like one book cannot be everyone's cup of tea. As an author you need to realize that. My point? You wouldn't do this in person, don't do it on your Facebook, tumbler, blog, twitter, whatever you use.
Best policy? Don't respond to the review or rating. Do not let your street team respond, and for the love of the writing gods do not stalk the reviewer! I can hear you now: But it's my personal page! I want to be real with my readers!
My answer to the first one: Yep, but this is the age of the internet, nothing is truly private. That's what's scary about it. Personal or not, you need to control your emotions and feelings. You are a business now, the way you act reflects on your product.
Second one: Be real with your readers, yes, let your readers know you're human to, but do that by interacting with them. Not ranting about them. I'm going to touch on that in just a minute.
Okay, so no responding to reviews. Next thing....do not go on some crazy rant about haters that you have. Seriously. We all have them, we all have people who say things mean about us or our work. Move along, for many of the same reasons above. You are going to hurt your brand if you react badly. This goes back to not ranting about your readers.
Interact with your readers, invite them to answer questions on your pages, they don't have to be related to writing or your books, they can be, but don't have to be. If they ask you a question, answer them honestly. (within reason of course) Even if the question is "What is the order of your series." You need to appreciate your readers, because without them you would be nothing.
Basically don't do anything online that you wouldn't do in person.