Its a matter of practice. When you are in Japan, be like a Japanese!
So the main thing is to become more polite when you talk with other people. Bow your head during greetings is another must do thing in Japan. Its quite amazing that all the Japanese people are so polite as this is the first lesson they learnt from the elementary school.
Try to take green tea. I know many of the western people do not like Green tea but you have to be used to of green tea as it is the must do culture in Japan.
Try to like the smell of Tatami room. Yes, I know many of you do not like it but you must praise the smell of a new tatami room. Smell of a new house is another thing you have to praise.
Whenever, you enter a room , do not forget to open your shoes and put it outside the room.
If you want to enjoy the Onsen (hot spring), you have to be remove all of your wearings.
Its hard but try to eat miso soup and fermented beans.
Use the formal dress whenever you will attend office or wedding ceremony or funeral.
Do not use the horn of your car! Do not change the lanes of the road.
The most important thing, always keep smiling even you are not happy in your heart but show the smiley face to the outer world.