Don’t use the chopsticks if they are uneven
Uneven chopsticks are considered bad luck as they are thought to resemble a coffin. Coffins are formed with uneven planks, some are short and some are long, that’s why using uneven chopsticks is believed to bring death.
Japan
Passing food from one chopstick to another is a taboo
It’s not the same as passing food from one spoon to another because in Japanese culture, passing food from one chopstick to another is similar to passing the bones of the deceased during funeral rituals. If you want to share your food with another person, simply place the food on their plate, so they can pick it up.
Don’t rub your chopsticks together
While in some countries doing this is acceptable because this is a way of removing splinters, Japanese culture would say otherwise. Rubbing your chopsticks together implies that you don’t trust the quality of the restaurant's cutlery.
Korean
Don’t hold your chopsticks and spoon at the same time
Koreans use both chopsticks and spoons during their meals. Spoons are used to scoop the rice and soup, while the chopsticks are used to pick up meat, vegetables, and everything else on the table. Holding both utensils at the same time is considered bad table manners, so you will see Koreans change from one utensil to another when eating.
Put your chopsticks on the table when you’re done
Never put your chopsticks in the bowl or plate when you’re done eating. Most especially, don’t stick it in your rice as this resembles the act of lighting incense for the dead. Once you’re done eating, you can place your utensils on the table beside your bowl.