Dear Wang Ming,
I'm glad to receive your letter. I'm happy that you're going to visit your American friend. When you go to an American home, you should buy a small gift, such as some flowers or some fruits. Could you get there on time? If you are late, the owners won't be happy. When you eat, you should say some good words to the dishes. You shouldn't stay too long. Would you mind my talking about these things?
Yours,
Wang Lei