Never tap your bowl with chopsticks -- it's how the homeless ask for food.
When eating dim sum, if someone pours you tea, always tap three fingers on the table as a sign of gratitude.
Don't pour soy sauce on fried rice, because it's already been seasoned.
It's considered rude to take food from a shared dish and put it immediately in your mouth.
When eating a whole fish, don't flip it over, as that symbolizes the capsizing of a boat. (via Jimmy Lee, Mikado)
When eating family-style and without a serving utensil, pick up food with the opposite end of your chopsticks; otherwise, you're essentially double-dipping. (via Nguyen Tran, Starry Kitchen)