From a college prof, this list of common, easily caught, cheating mistakes is amusing. I tend to give less papers and more problems, so I don't see all of these, but they're definitely similar to things I have seen. *Sigh* As a commenter says, if you're good enough to cheat right, you probably don't need to cheat. It's probably more effort to actually do those things, than to do the work in the first place!
ETA: Whee, I just got to delete a spam comment for an essay writing webpage! (Same as someone legitimately commented about below, but this one was clearly spam.)