Or how to slay that nasty dragon called plagiarism.
Or in other words, "Thou Shalt not Steal" (Exodus, 20:15, KJV).
There are lots of great resources out there to help students, and other writers, understand what plagiarism is and how to avoid it. Here are a few quick links to help the average librarian get the point across.
For an all around writing course and citation how-tos try the Online Writing Lab (OWL) at Purdue University.
If you need help formatting a citation correctly Son of Citation Machine will help you plug in all the information and generate full citations and parentheticals for all the standards citation styles.
Kate Hart has created a great info graphic on her blog that's geared toward helping bloggers cite and link to sources correctly.