Visiting Japanese Friends For Dinner :)
If you have the opportunity to go to a Japanese friend's house, you should know about Japanese culture such as the table manners. Japanese people always use chopsticks but don't worry if you can't use them, you should just try to use them and then ask your host/hostess how to use them.
The most important thing is you mustn't stick your chopsticks in your rice because people do this at funerals. When you start eating, you should say 'i ta da ki ma su'; which means thank you for everything and when you finish it you should say 'go chi so u sa ma de si ta'; which means the same. I think these words have a more profound meaning so your host/hostess will be glad to hear them.
Although you should know about Japanese table manners, more important things are to enjoy spending time with your friends and enjoy having Japanese food!