When Traveling to Japan
They will go out of their way to make sure you are comfortable. Please do not take advantage of this by asking for too many things. Have some common sense and courtesy.
Learn to Bow
This is important. Japanese are big on bowing. Do that instead of shaking hands. It shows respect to their culture. While there are certain rules to follow when bowing if you are Japanese, don't worry about it too much as a visiting foreigner. Just do a 1 to 3 second bow and people will be happy.
Learn to Use Chopsticks
They'll be impressed if you can use them to feed yourself. They will be kind in offering you a fork, but, to me, that defeats the purpose of learning the other culture.
Leave the Ego at Home
Japanese apologize a lot. Not because they are weak, but because they are showing deference. They are showing you honor. Do the same with them. It doesn't hurt you and it helps ease relations.
Get Google Translate or a Phrase book
Put Google Translate on your phone. Do not write out long sentences. That will only confuse things. If you need a seafood restaurant, just type in "seafood restaraunt" not "I'm looking for a seafood restaraunt, can you show me where it is?"
No Trash Cans
It is considered unusual to be walking while drinking or eating. It's also rude to try to throw away your trash at a stand where you did not purchase that item. Most places will not accept the trash. Eat where you bought the item, then throw away your trash there. You will not find trash cans on the street, either.
7-11 is Your Friend
If you're hungry or thirsty and you need something quick, if you need a white collared shirt, if you need socks, if you need cash from your American bank account, go to 7-11.
No Paper Towels
When you go to the restroom, it's best to have your own small hand towel. You will not find air dryers or paper towels in most public restrooms.
Use them, you will be happy.
If you have tried it in the Unites States and you found that you did not like it much (like me), I would suggest you try the truly Japanese sakes. They are fantastic!