1.) It's bad to "lose face." Under this rule, it's better to tell someone that you will take him to dinner sometime and then just not do it than to say, hey sorry I'm too busy. Also, it's better to just avoid the subject of a change in plans and then if the other person doesn't mention the thing you had previously planned to do tomorrow, you just assume it's off. To ask about it would be to make them lose face if they couldn't go.
2.) It's ok to have your phones out during class or important meetings, and send text messages or even quietly answer a call.
3.) I don't know how to generalize this, but this week, the cleaners in our buildings were required to put up emergency exit signs on a specific spot on the inside of our doors. Many of us had things on our doors and were sad. But the lady putting it up in my friend's room took down her poster, put up the emergency exit sign, and promptly replaced the poster so that you couldn't even tell the sign was there. I guess she followed the directions. . .