Plagiarism-It's a bigger issue then I thought

When it comes to plagiarism, it's clear that it's bad. But, my biggest issue with it is how do you cite correctly so you don't have to plagiarize to begin with. If you do the citation wrong it's still considered plagiarism. And, my question is, whenever you copy a paragraph do you have to cite every single sentence or just quote the whole thing? There are so many exceptions to plagiarism it's hard to keep track of everything. And, as the age of the internet is evolving so much, plagiarism is obviously becoming more of a problem. Donald J. Dudley says, " Writing is difficult, and doing it well takes time and practice". But that doesn't mean stealing someone else's work is going to help your ability to write.
I kind of always thought that maybe I just didn't learn how to cite correctly in high school or maybe I just didn't understand how to do it, but now in college I never thought how big of an issue plagiarism was because it was never stressed as much in high school. Sarah Wilensky said, "If you're taught how to closely read sources and synthesize them into your own original argument in middle and high school, you're not going to be tempted to plagiarize in college, and you certainly won't do so unknowingly". My point exactly, learning how to not do it and cite correctly. Another issue, are middle and high schools slacking on teaching students how to cite correctly. It is clear it's an issue, and now it's just learning how to cite correctly so I'll never have the problem of thinking, did I plagiarize?