There is a totally different idea of what teaching is and what respect is to teachers in Vietnam:

1. Students very reverently stand and greet the teacher at the beginning of the class. Then they sit town and talk to each other and ignore what the teacher is saying. American teachers, who are accustomed to students actually paying attention to what they are saying (teachers in grades K-12 would lose their jobs in California if the kids acted like Vietnamese kids!)
2. The Vietnamese teachers teach English wrong. They always write dates with suffixes (i.e., July 11th, 2008), When written properly (i.e., July 11, 2008), the students will almost throw tantrums about the fact that you teach English and you don't even know how to write dates.
3. To me, many Vietnamese seem absolutely rude. If the supermarket is crowded, they actually push and grab people to get through. Children can be disrespectful to the point of causing terrible accidents and the parents respond, "Oh, isn't that cute."
4. Too many jobs are of the verbal contract type... no written promises. Remember this, a verbal contract isn't worth the paper it's written on. There are jobs I've done that I've waited almost two years to get paid. I know I never will get the money.
5. If you teach in a language center and they give you 15 minutes to teach anything you want (with no forewarning), you might want to reconsider if you give a lesson in American manners, such as how rude it is to ask about age, income, race, politics, and religion. The Vietnamese teachers work with the students so they can ask you those questions.