Teaching about Cheating
What some students forget is that if they can find an article to steal from, I can probably find it, too. When I edit assignments, I plug random quotes, clauses, and full sentences into search engines to check for similar word patterns. I look closely at poetic turns of phrase or quotes that seem too good to be true and verify the names of all sources and affiliations. If I can't confirm the existence of a source used in a story—say, she isn't on Google, Lexis-Nexis, 411.com, or Zabasearch—I tell the student to provide contact information, and I then call or e-mail that person."
From "Me Against My Students - How I use the Internet to combat plagiarists, fabulists, and cheaters," by Adam L. Penenberg, in Slate: http://www.slate.com/id/2127365/.
Here's a teacher doing the right things. He's reading his students' writing and getting to know their style and voices. He can use search engines as ably --if not more proficiently-- as can his students. He lets them know that he can. He's considered Turnitin.com, but sees it as too blunt an instrument (which it is).
What this article is also about, however, is a journalism instructor acting towards his students as a good editor would act towards his reporters. That is, sources are confirmed and facts are checked. The editor/instructor reads closely, knowing their reporters/students. Ethics are stressed and practiced and steps are made to keep folks ethical --double checking, reading closely-- yet the methodology isn't heavy handed -- using something like Turnitin.com blindly.
And patience. When you read Penenberg, you sense a good deal of patience and care in his prose and voice. I think that's key to successfully teaching students away from plagiarism.