My strategy for plagiarism is to attempt to give students very specific assignments that can't be found online (I doubt there are too many papers comparing Flight to Canada and Mrs. Dalloway but I could be mistaken). I also have weekly papers due so I can learn my students' writing styles. Since I am/have been a composition instructor for the last few years, I have a good ‘ear' for plagiarism also. I am able to notice shifts in diction that do not sound like something a student would use or know.