Numbers
4 (sì) sounds like "death" — some elevators skip the 4th floor. 8 (bā) sounds like "prosperity" and is the luckiest; 6 means smooth; 9 sounds like "long-lasting".
Colors
Red means celebration; white is for funerals (never give white flowers except at a funeral); gold means wealth. Avoid all-white or all-black gift wrapping.
Gestures
Pointing at people with your index finger is impolite — use an open hand. Give and receive with both hands. Patting an adult's head is rude (the head is considered sacred).
Topics
Avoid asking about age, income or marital status on first meeting — even Chinese people find these intrusive from strangers. Steer clear of politics.
Tipping
Most places in China don't accept tips — restaurants, taxis, hotels. Some upscale venues add a service charge instead.
Miscellaneous
Blowing your nose loudly or picking teeth in public is impolite in formal settings. Sitting in the back of a taxi is common. Chinese-style politeness sometimes means refusing an offer three times before accepting.