Check out this handy dandy plagiarism flow chart. I used it in class recently. It definitely helped my students thinking about when to cite and avoiding any plagiarism issues in their work. The chart is from a really good site on plagiarism and the IB Extended Essay.
Many of the teachers that come to this site teach in an International Baccalaureate (or IB) school. The IB has rigorous academic honesty policies for their classes. For example, all IB teachers must sign off on the originality of each of their students work. For this post, I have collected a couple of IB resources that discuss effective practices and principles to utilize in your classrooms to encourage academic honesty. By no means are these documents limited to IB teachers, all teachers should find them useful.