Understanding plagiarism and song ownership issues so you don't look like a fuckhead on the Internet

A couple years ago I wrote this post and then this other post about plagiarism in k-pop, to help the people I encounter understand the basics of what plagiarism is and is not.  I still gets tons of questions every time a new k-pop plagiarism or song ownership dispute appears, which seems to be about once per week lately.  So in the spirit of "teach a man to fish rather than slap them across the face with a fish", as well as the spirit of "please stop asking me these stupid fucking questions because nobody cares", Kpopalypse now brings to you a nice, simple guide to finding plagiarism in your favourite k-pop songs!  Yay!