Social Media tends to be a place for anyone to voice their opinion on any matter and hardly ever thinks twice about the ramifications. As a result of this, larger companies often employ their own lawyers to go over any campaign that a company might want to run to make sure that the company can't get sued or worse.
Small businesses don't have the luxury of hiring lawyers whenever they want to produce a marketing campaign, but that shouldn't scare you away either. The nice thing about social media is that if it's an honest mistake there can be grace. For example if you post a picture that you don't have permission to use and the owner finds out, then you'll probably just get a DMCA (Digital Millennium Copyright Act) takedown notice. This is kind of like a cease and desist order from the FCC in radio or television.
However, it is always better to provide a source of where you find things that you post that aren't your original work. The links that you create can also help you in Search Engine Optimization, so not only are you doing the right thing, you are sort of getting a slight reward out of it. Most of the time, no one will probably ever say a word because let's face it, the Internet is a big place and your small business probably isn't trending on social media. But just because no one may find out about it doesn't make it ok to do it. It's still illegal.
Where things can go really bad for you in the social media realm is when you make comments that are religious, political, racist, sexist, homophobic, and the list goes on. Stating your opinion on matters that probably have nothing to do with your business or what you're selling should just be off limits. These kind of comments can spread like wildfire and ruin your reputation and destroy your business. Just because you may have a freedom of speech doesn't mean you should exercise that right without caution.
A good thing to remember is that Social Media is organic and unpredictable. You can never assume that people will respond a certain way to what you release to the world. For example, McDonalds started a hashtag called #McDstories with the thought that people would tell about the great memories they had going to McDonalds. It ended up being more about the horror stories of McDonalds and the campaign quickly tried to shutdown, but it was already out there and you can't control what others say. Fortunately for McDonalds, they have a lot of money, so they can get through these kinds of fiascos that your small business most likely can't.
Now let me just try to clear this all up and simplify it. Think before you post anything to social media, if you have any doubts, then don't do it.
Link to sources that you use, whether it is an article, photo, video, chart, etc.. It is always good practice and it shows integrity and validity.
Lastly, don't be afraid to ask for help. Social Media is an ever changing monster that will never really be tamed. If you can think about it that way, then you generally be ok.