1. Filling Your Own Glass
When drinking alcohol with Japanese friends, it's considered rude if you are only filling your own glass. In Japan, it is proper etiquette to refill everyone else's glasses and not your own. If you fill someone else's glass, they'll return the favor and fill yours too.
2. Taking the Back Seat
If you're catching a cab solo in Australia or New Zealand, remember to always take the front seat. Sitting in the back will make the cab driver think that you're a stuck up passenger.
3. Doing the Thumbs Up!
Doing the thumbs up is a positive gesture which means OK to most of us. But in other countries like Australia, Greece or the Middle East, it means “Up yours!” So better keep your thumbs to yourself.
4. Eating With Your Left Hand
If you're in the Middle East, India, or Africa, be careful not to use your left hand when eating and passing food – only use the right. The left hand is known to be unclean and used for matters done in the bathroom, so eating with it will probably give you unwanted stares from the locals who've already lost their appetites.
5. Say America!
If you're an American and you're in South America, remember to answer USA or United States when someone asks you “Where are you from?”. Saying “America” makes it look like you're only referring to the USA as the only America when there's also South America. Clear?
6. Send Even Numbers
If you want to send flowers to a friend in Ukraine as a romantic or friendly gift, make sure you give an odd number of flowers. Sending an even number of flowers is only meant for funerals.
7. Showing the Peace Sign
If you're in the United Kingdom or Ireland and you want to indicate you want two pieces/orders/etc. of something, make sure that your palm is facing outwards when you do the V-sign. If you do the opposite way and face your palm towards you, then you're asking for trouble because that simply means “F*** off!”
8. Showing Your Soles
In India, the Middle East, and other parts of Asia, displaying the soles of your feet can be considered as an insult for the locals, who see it, because the feet, especially the soles, are often perceived as unclean. So don't show those soles and remember to remove your shoes before entering someone else's house.
9. Sticking Chopsticks in a Bowl of Rice
In East Asia, sticking your chopsticks vertically in a bowl of rice is considered taboo and bad luckbecause this is a sign of death. This is only done during funerals.
10. Giving Tips
You might get used to paying tips when you're from/in the United States but in other countries it's not expected and sometimes may be perceived as an insult, like in Japan and Korea.