In western nations, making noise while you eat is considered annoying and improper, but it's the opposite in the East. In Asian countries, loudly slurping your soup or noodles is a compliment to the chef.
Although giving someone a thumbs up is a sign of affirmation or approval in many places, the people of Italy, Greece, Nigeria, Afghanistan, and Iran will not be so pleased to see it. In these countries, the gesture translates to "up yours," and is seen as very offensive.
Even though being "fashionably late" has become a trend in America, Americans still recognize that the polite thing to do is to show up on time for a planned event. This isn't the case in Argentina. Showing up on time there is seen as rude. Instead, guests are supposed to show up 30 to 60 minutes late.
You probably thought that a smile was a universal sign of happiness, but it can mean something different in Korea. Smiling at a Korean stranger is very offensive — it means you think that they are unintelligent.
It's a very nice gesture to compliment someone's belongings in most places, but it's a rare act in certain African and Arab countries. If you tell someone in one of these areas that you like one of their possessions, they may feel obligated to give it to you.
Front Seat Taxi
You're probably used to getting into the back seat of a cab, but that if you do that in the Netherlands, Scotland, New Zealand, or Australia, you'll be seen as stuck-up. In those countries, it's polite to take the front seat next to the driver if it's available.
The Japanese have a whole set of rules of etiquette for exchanging business cards, and deviating from it is very insulting. When given a business card from a Japanese man or woman, you should hold it with both of your hands, thoroughly read it, and then be sure to put it away with care.
Right Handed Dining
In many eastern countries like Morocco, India, and parts of the Middle East and Africa, it is considered rude to eat your food with your left hand. The reason for this is that meals are frequently shared among a community, and the left hand is reserved for unsavory taks like using the bathroom.
Although making a peace sign or asking for 2 of something is a relatively harmless gesture in America, it's not so in the UK, Ireland, Australia, South Africa, and New Zealand. In these places, the V-shaped gesture is similar to the middle finger, but only if the back of your hand is facing them. The gesture isn't offensive if your palm is facing the person.
In Asia, India, and the Middle East, it is considered offensive to show someone the soles of your feet. If you do walk around barefoot in these areas, you should be careful the bottoms of your feet never face another person. Actively pointing the soles of your feet at a person is considered one of the rudest gestures.
You may want to refill your glass if you're still thirsty after finishing off a drink, but refilling your own glass is actually an etiquette no-no in Japan. Instead, you'll have to wait until someone notices and offers to refill your cup. Perhaps top off someone else's drink and hope they return the favor.
It's not bizarre for an American to call someone over to them by curling their index finger upwards, but this gesture is seen as rude in many areas if East Asia. The gesture is only used for dogs in these areas, so if you use it on a person you are equating them to a dog. It is especially offensive in the Philippines.
Count the Flowers
You could wind up really offending someone in Russia or the Ukraine if you send them the wrong number of flowers. While bouquets with an odd number of flowers in them are a beautiful gift, bouquets with an even number of flowers are reserved only for funerals.