In Asia, never touch any part of someone else's body with your foot, which is considered the "lowest" part of the body. If it happens accidentally, quickly apologize by touching your hand to the person's arm and then touch your own head. And don't point at objects with your feet or prop them up on chairs.
Never ruffle a person's hair in Asia, either. It's the most sacred part of the body.
Shaking hands across a threshold in Russia is considered unlucky. Wash your feet before entering a Japanese bath -- not to do so is like peeing in an American pool.
And for business travelers in Brazil, don't be offended if a client answers his cell phone in mid-conversation with you. Not to do so is rude. But you can be up to 30 minutes late for an appointment -- that's common. And never insult the royal family in Denmark; it always offends everyone else.
Reid dispels the myth of the ugly American, but for inexperienced travelers, remember that it's attitude that counts.
"Open yourself up to different cultures and learning," said Reid. "People make mistakes. If you walk into a Buddhist temple with your shoes, and they ask you to take them off, don't say, 'Gosh, that would never happen in my Presbyterian church at home.'
"If you are understanding and apologizing and respectful, you learn something from it. People make mistakes, and it's OK."