When you visit someone in Japan, it is polite to take a gift. Remember to take your shoes off as you enter the house - they will give you special slippers to wear instead. Leave your shoes at the door, but make sure the toes are pointing towards the door. When you are in the living-room, don't sit anywhere you like- wait until someone shows you where to sit. Also, don't blow your nose in public- find a place where you can do it alone.