Japanese superstitions

    * The number four:
      The number four is considered inauspicious because it is pronounced the same as the word for death (shi). Therefore, one should not make presents that consit of four pieces, etc. In some hotels and hospitals the room number four is skipped.

    * Stick chopsticks into the rice:
      Do not stick your chopsicks into your food generally, but especially not into rice, because only at funerals, chopsticks are stuck into the rice which is put onto the altar.

    * Give food from chopstick to chopstick:
      This is only done with the bones of the cremated body at funerals.

    * Sleeping towards the North:
      Do not sleep towards the North beacause bodies are laid down like that.

    * Funeral Car:
      If a funeral car passes you should hide your thumb.

    * Cut nails at night:
      If you cut your nails at night, you will not be with your parents when they die.

    * Lie down after eating:
      If you lie down immedeately after eating, you will become a cow.

    * Whistle in the night:
      If you whistle in the night, a snake will come to you.

    * Black cat:
      There are also some imported superstitions such as the believe that black cats crossing the street in front of you cause bad luck.

Let’s also add putting chopsticks up your nose.  Probably frowned on by the Japanese.

From japan-guide.com via