jennin64

If you invited the guests to a meal, you are responsible for the check.
若妳主動邀請妳的客人去吃飯,妳就要負責付帳
 (我還沒聽個這種規定或習慣)
If  (it is) a joint meeting, ask at the beginning or when scheduling the lunch on check splitting. 
 若是工作餐會(邊吃邊開會,像是午餐會報),妳要在 會前 或當妳預定這會議時間表之前協調付款方式(split the check = 各付各的 = go dutch)

A personal handwritten follow-up note is also appropriate.
 在會議之後的一個手寫的非正式感謝函(hand written follow-up note)也是OK.
Sending flowers in advance relieves your host or hostess from taking care of them when you arrive.
 在妳到達之前 事先寄花(花圈花環花牌?)會讓主人(有時間在妳到之前處理花)在迎接妳的時候比較不忙(不必同時處理妳的花兒)
If someone gives you a gift, you do not have to give one back. To feel obligated to return a gift with a gift embarrasses both giver and receiver. 
 收禮不必回贈 逼自己回贈 只會破壞(送者與收者之間的)感情

以上是我自己翻的 想請問有沒有更好的解釋? 謝謝
 Please let me know if you can better my work.  Thanks. 

我只是天成翻譯社而已 有些禮俗 並不正確 也可能違法(US anti-corruption laws)