When you're invited to have dinner at a foreigner's home, please remember the followings.
At the table, when the hostess(女主人) picks up her napkin, you may pick up yours and put it on your legs.
If a servant(佣人) passes food around, he will pass the dish to you at your left hand so that you can easily serve yourself with your right hand. Never serve yourself while the dish is on your right. It is then the turn of your neighbour on the right.
Do not reach across the table to get something in front of someone. That is not polite. Ask him or her to pass it to you.
There are things in the middle of the table, such as bread, butter, and candies. You shouldn't take any until the hostess tells the servant to pass them to you.
Do not leave your seat without saying anything. If you need to leave the table to go to the washroom or do something else, you should say “Excuse me for a moment, please.”