One possible version：

Dear Jack,

Glad to receive your e-mail and you’re welcome to China. The following are some Chinese social customs.

Firstly ，we greet each other by saying “hello” or asking such questions as “where are you going？”or “are you busy？”to’ show our concern 。secondly，when praised ，we reply with “oh，no！”or “I’m over –praised”to be modest 。finally，at dinner parties，we talk loudly and touch glasses when drinking to someone’s health or success to express warmth 。usually，we drink as much as we can，which indicate we’re good friends and the host will be more pleased if we do so。

In short ，there are many differences between American customs and chinese ones。If you do as our chinese do，you’ll enjoy your stay in china。

I hope my suggestions will help you a lot and that you’ll enjoy yourself at your friend’s wedding party.

Yours,

Li hua