In Russia, Greece, Iran, Sardinia, and parts of West Africa, you give thumbs up.
impolite (the equivalent of flipping someone off).
In Mexico, you arrive late.
polite (In fact, it is considered rude to be early or on time for an event and being up to 30 minutes late is the norm).
Touching someone's head in thailand.
impolite (Thai people believe that the head is where the soul resides).
In Egypt, you wait until the oldest male has started eating.
polite.
Tongue out in Tibet.
polite (It's seen as a greeting).
In Korea, give things to others with two hands.
polite.
In Chile, use your hands to eat.
impolite (a proper etiquette requires eating everything with a fork and knife).
In Afghanistan, people kiss fallen bread.
polite (to show appreciation for food)
Tipping in Japan.
impolite (Instead of tipping, they left Origami Tip or bow and smile to say goodbye to staffs before leaving).
In India, eat with your left hand.
impolite (the left hand is seen as disgusting).
Chinese people will refuse three times before accepting a gift.
polite (This is just their way of showing humility).