Normally I wouldn’t notice if anyone was cheating, but one time, I was sat on a stage, doing my exam and I couldn’t really miss watching the others. That particular time 2 foreign students got kicked out the exam for talking and another for having notes stuck to the back of a ruler.
I taught an engineering course a few years ago. On one homework assignment, several students turned in work that had obviously been copied from the instructor’s solutions manual. I asked these students to stay after class and said, “Well, I graded your homework, and I want to let you know that I, too, have a copy of the solutions manual.” Every face whitened. I believe this was due to our university’s very rigid policy on cheating and plagiarism (it was a big state school famous for its football program. And yes, it was recently in the news because of allegations of cheating by a very prominent “student-athlete”).
I chose to give them zeroes on the assignment with a warning that I’d be watching them like a hawk and another questionable incident would result in a failure for the course and a referral to the academic violations committee. I was pleasantly surprised that almost all the cheaters apologized profusely later, in private. I got the impression that they were actually appreciative that a teacher was paying close enough attention to their work to detect cheating.
The only real cheating issue at my school, as far as I know, is the fraternities. At least a couple of them carry extensive archives of old material (some of which has been released by the professors, some of which has been specifically forbidden from being released), often attempt to obtain current exams in advance for key classes, and also have archives on common paper topics to help their members.
As for “during the exam” type cheating, I have yet to see a case of it in a year and a half here. Almost all non-essay exams have multiple forms, and the proctors generally watch very carefully, especially in the larger classes.