7 gestures to get you killed overseas

1. Extend Your Hand, Palm Outward in Greece: I would like to shove s**t in your face.
2. Finish Your Meal In Thailand / The Philippines / China: you have not given me enough food.
   
3. Give the Thumbs-Up In The Middle East: I would like to shove my thumb up your a**e.
4. Say "Hi" to a Member of the Opposite Sex in Saudi Arabia: I would like to commit immoral acts with you.
5. Give an Even Number of Flowers in Russia: it's your funeral.
6. Give a Gift With Your Left Hand in India, Sri Lanka, Africa and the whole of the Middle East: I give you this gift with the same hand I use to wipe my a**e.
7. Give the "OK" Sign in Brazil: equivalent to giving someone the finger.
   

From Cracked, although I'm not sure how helpful it is in list form. It's hard to remember. Best to only look at the entry that applies to your destination, blocking the others from view.