The best way to deal with plagiarism is to prevent it rather than to play cop and catch and punish the culprits. The latter role is a nasty one. Few of us, I suspect, have much relish for it. It is far more rewarding to be, as we say nowadays, pro-active, and prevent the practice of plagiarism. But how?
An effective method for doing this comes from following one of our most basic principles about academic writing. Many of us profoundly believe, teach, and preach that writing good academic essays is a recursive process. That is to say, essays are written in stages, and our minds are always going back and forth among these stages in the messy business of creating an essay. If we simply follow through on the implications of this idea in our own classroom and tutorial work with students, we can cut down the very temptation to plagiarize and thus go a long way to eliminating the odious practice itself.
The major steps in the writing of an academic essay are these:
Asking students to hand in the various stages of the essay while they are working on it works. Part of a faculty members job is to comment on the work in progress, to get back to students with suggestions about these various stages. Sleazy commercial essay providers will not be interested in selling the early stages of the essays. Nor can there be much of a buyer's market here. It is a simple matter for us to look for some connection between the earlier stages of the essay and the finished product that is handed in for marking and grading. More significantly, it should be satisfying to us to help students learn to go through the process of writing. And it should be very useful to them to acquire the habit of working through such a process.
A variant of this technique that a colleague has used is the instruction to hand in with the final essay, all of the rough work that preceded the final copy.
Finally, students must be reminded that theoretically we do not consider any essay that is handed complete unless the student can come to the professor's office and explain and defend any part of the essay, any idea, phrase, word, or the essay as a whole. Hopefully, this is a last resort and won't have to be used often if ever. On very rare occasions, however, when it was necessary to do so, there is the usual expected unpleasant result. The chief value of the idea is as a deterrent. This threat is a negative technique; and it is preferrable to use the positive approach: working with students in the stages of their essays, as a way of encouraging and helping them to become more effective writers.