Since I slept so much in class, I understand when someone sleeps in class. Someone made the effort to come to class, but now that they're there, they can't keep awake.
I don't mind if people come into class late. If they miss anything important, that's their problem, but it doesn't bother me.
I don't mind if there is a bit of chatter in class, as long as it doesn't get out of hand.
But if my students have math homework to do or they want to read the newspaper or text message, they need to leave. I let them know this on the first day of class. When someone does something like this, I have a strong reaction. It is something like, "Go. You must go now. I have no problem with you doing that, but you must go now and do it somewhere else."
I only lost my temper once, in class. About 17 years ago I decided to give students some sample problems to work in preparation for a test. Mr. P. did not do as well as he wanted to on the test. And he was upset that I had given the questions, but had not given the answers. I explained that I was not obligated to give any questions, much less the answers. Few, if any, teachers were giving as much assistance as I had given. I should have said, "Thank you for your input. And now we move on." But I kept trying to explain it to Mr. P., who was really just saying anything to avoid saying, "I'm ticked off because I got a bad grade."
I got frustrated. I lost it. Threw chalk against the wall beside me--not in the direction of the students. Chalk particles showered the area. I said, "Let's go home and try this again next time."
I was worried that my end-of-semester teaching evaluations from that section would be low. I got the highest evaluations from that class that I had received up to that point.