A few tips are;
1. Be polite.
2. Don't tip restaurant waiters, it's an insult to them.
3. If you eat ramen/noodles, slurp and be loud. it shows you enjoy the taste.
4. When you say 4 in Japanese, its either yon or shi. Don't say shi cause it also means death.
5. Don't open doors for others.
6.Japanese people are generally nice and will help you. Don't be shy if you ask for help.
7. If they bow, then you should also bow.
8. If the word gaijin offends you, remember it's not always offensive to the Japanese people who say it cause it basically means foreigner. It's literal translation is outsider which you are.
9. If you order food in a restaurant, then don't ask for changes in the food. Like ordering a chicken mayonnaise sandwich without the mayonnaise. They'll think like, why did you order something which you don't like.
10. Cause your a foreigner, you will make some mistakes, just say Gomen'nasai if you mess up. It means sorry. It shows you care for the Japanese culture.
11. Sneezing in public is looked down upon. It's also looked down upon in other countries too so Japan isn't the only one.
12. If you enter a convenience store, the workers might bow to you, you don't have to bow back.
13. Japanese people are really nice. If you leave something like an umbrella somewhere, no one will take it.
PS most foreign phones don't work in Japan. Get a new phone if you ever visit Japan.
Here is a link to more Do and Don't in Japan:
http://www.japanguidebook.com/102-must-know-dos-and-donts-of-japanese-...