TL;DR: You must use and attribute the Creative Commons source in the exact same manner you would any other copyrighted source. That means you can’t claim the content creator’s work as your own or redistribute it in its whole for money. But citing it with attribution or any other form of Fair Use is a-ok. If you’re not sure if your use would be deemed Fair Use in a court of law, either seek permission from the source or ask a lawyer who knows.
All that Creative Commons does is provide rules for distribution and reproduction without asking for permission from the copyright holder first. In the case you cite (CC BY-SA) you can share (SA) the work in question, in its whole, with attribution (BY) so long as that platform is also a Creative Commons Forum.
But you aren’t distributing that work in its whole; you’re citing it. (Probably. If you are distributing that original work verbatim and adding onto it you can actually do that. You just have to attribute the source and you can’t do it for money.) That means you’re using it under Fair Use.
And while a court of law is the final arbiter of what is considered Fair Use, there are some guidelines you can go by. If the source is fictional then comment, criticism and parody are all (generally) considered Fair Use. If the source is non-fictional then the rules are much looser, since the dissemination of facts benefits the public. Using your source in way that benefits the public interest is almost always considered Fair Use.
So why all the hubbub about the proper use of Creative Commons? Well, on sites like Stack Exchange, and Flickr there is concern about one thing - selling your creative work after it appears on a Creative Commons site. That is where things can get a little muddled. But the general consensus is that the content creator retains ownership (copyright). That means if I post an excerpt of my book on Writers.SE I can go ahead an sell that book to a publisher for money but that publisher might hesitate to commit since they can't be guaranteed exclusivity of at least a portion of that content. That's because someone, like you, can redistribute my excerpt freely without my consent as long as you attribute the source (me & SE) and not take money for it. But I'm getting off topic.
Please don’t take anything you read here as a substitute for legal advice. If you have questions on something that you feel could potentially cause you legal troubles, contact a lawyer that specializes in copyright issues (or whatever your local designation for ‘legal representative’ is).