When my students violate academic honesty, they are not sinning against me; they are sinning against the standards of an intellectual community they have agreed to join. The proper response is to follow the standards that the community has established for such offenses.
So, no private lectures delivered without a punishment, no slaps on the wrist. Document the offense, fail the student for that assignment, and/or require completely new work from the student. Keep it all on the record in the event of future offenses.
Sure, I still get angry when I discover a plagiarized paper — I even get angry at plagiarism cases I hear about secondhand, like my colleague's. If you feel anger, you feel it. Sometimes that can't be helped. But feel it and let it go. And don't address student violators with anger. After all, it's not about you.
Exactly right: let the system work the way it's supposed to work but leave the vindictiveness behind. (He quotes a colleague who wants to exact punishment beyond that dictated by the university.) This assumes, of course, that your institution has a system that works and not one where you have to wait until the student agrees that he or she plagiarized or until hell freezes over, whichever comes first, before anything can be done.
I know colleagues who threaten an F for the course but then give plagiarizers a stern talking-to and then let them rewrite the paper. This doesn't make sense to me for two reasons. First, I'd think that word would get around that you don't mean what you say. Second, this system punishes me instead of the student, since I have to burn my Friday evening tracking down the sources and then (insult to injury) have to regrade the paper. No, thanks.
I get angry, too, but my approach is like Lang's: there's a punishment listed on the syllabus (an F for the paper and a report to the appropriate office of student affairs). I explain to the students what's going to happen in a very matter-of-fact way. It's a hit to their grade, no question, but if they shape up and work hard, they can still pass.
Sometimes there are tears and sometimes not, but the point is that they might learn something from the experience. At a minimum, they learn that I can find my way to Wikipedia and Google, too, and if things go well they learn that there are consequences, but not irremediable ones, when they screw up.