Did you all hear when he said? I want to make sure everybody heard it correctly, because I intend to file a complaint. 

I would like you all to take out your papers and begin when I say "Start." 

If you all take three cookies, there won't be enough for the guests.

In these examples, either "all" is emphasized or else given the same weight as "you." It's important to the meaning of the sentence. 

   Southerners, on the other hand, tack "all" onto "you" where other speakers would simply use "you" and let it be assumed to be plural. 

I'm sick and tired of y'all bitching about everything I do. From now on y'all can do your own laundry.

Do y'all want to go to the movies, or just hang out around here? 

Y'all, I swear, this has been the best birthday I've ever had. I love y'all so much. 

They don't say "you-all" where I live, but as I understand it, this would be pronounced with the emphasis on the first syllable, distinguishing it from "you all" without the hyphen. 

Important Note: contrary to what you might see written or filmed in depictions of the American South, "y'all" is ALWAYS plural. ALWAYS. In fact, while other English speakers have to deal with the ambiguity of "you" being both the singular and plural pronoun, Southerners do not.

I heard y'all were moving, but then somebody told me you were going to stay here and finish your last year of school.