The more popular Japanese (and Asian) food becomes worldwide, the more people use “hashi” (chopsticks). Like western table manners, in Japan there are also ways to use chopsticks properly. I would like to introduce some bad manners when handling chopsticks, so please be careful to avoid these!
You should not split waribashi (disposable chopsticks) in front of your face, and you shouldn't rub the chopsticks together.
You should not wave your chopsticks above food.
You should not touch a piece of food with your chopsticks and then not pick it up.
You should not use the chopsticks to spear food.
You should not stick your chopsticks straight up in a bowl of rice.
You should not pass food directly from your chopsticks to another person's chopsticks.
If you want to know more details, please take a look at the following reference
By the way, when you eat sushi, you can use hands instead of chopsticks if you want to. (You don’t need to use chopsticks.) Eating sushi with hands is not bad manners! No worries.