Namely, Japanese seem to be resistant to reusing chopsticks, and people are far more comfortable with disposable chopsticks than reusable alternatives (unless they are using their own pair). Chopsticks become strongly associated with the person that uses them. On the eGullet thread, I suggested that the origin of this is in old taboos about touching other peoples’ belongings, and also tied to Shinto rituals related to chopsticks.
Actually, although Japan has a reputation for elaborate ritual, it’s not so difficult to learn basic Japanese dining etiquette. Most of the rules about how to behave when eating are just related to chopstick usage.
You don’t need to worry about the order of utensils to use since there’s usually only one to choose from. You don’t really need to worry about where your left hand is. You don’t even need to worry about the order of what to eat, although it’s more delicate to take a bite of rice, when present, between tastes of different side dishes.
I think you need to worry more about whether you have holes in your socks than the way you eat.
Gourmets may argue about the preferred order to eat certain foods, but it’s not necessary to follow such rules to be polite; it’s sort of like knowing the preferred order to eat cheese in the U.S. or Europe. It might reflect on your sophistication or lack thereof, but doesn’t make you a barbarian.
I have sometimes tended toward nervousness when eating with unfamiliar people in Japan, perhaps from some anxiety that I may do something inappropriate. This is perhaps slightly amusing or occasionally endearing but completely unnecessary. Except for some easy-to-follow rules about manipulating chopsticks, you don’t need to worry much.