A guide of what to do with chopsticks and what not to while in Japan or a Japanese Restaraunt...
5 things never to do with o-hashi
1. Never play with chopsticks. Using them to drum on the table, have mock sword-fights or such is ill-mannered.
2. Never pick something up with your hand without putting the chopsticks down.
3. Never pass food from one pair of chopsticks to another. This is a horrendous faux-pas.
4. When using the cheap, disposable chopsticks called "waribashi", which one pulls apart like a wishbone, do not rub the ends apart to remove splinters. By doing this you would be saying, "Your chopsticks are so poor I fear I may harm myself on them."
5. Do not dip your chopsticks into your water-glass before eating.