culture shock!!!

When i came in NY, I was really confused about that somebody asked a question such as Aren't you coming to the birthday party? Koreans answer "yes" when they really can't come. So...Always, my answer was really opposite of what they understood.  That's why I was very confused.
Our way of using yes and no when answering negative questions in the Korean language is the opposite of yours. Koreans say yes or no based on whether we agree with the meaning of the whole sentence, not based on coming or not coming as in English. We answer yes to the question Aren't you coming to the concert tonight? when, in fact, we aren't planning to come. That's because when speaking English we are often confused by our mother tongue.
The other thing is that Koreans rarely call each other by their first name except for close friends and children. When i started to study in NY, students call professor's first name naturally.
In Korea, it's not as common to call others by their first name as it is in many other countries. Though students often do use first names among themselves, adults only use first names with their closest friends. At other times, we call people by their first name together with Mr./Ms. This is very common among colleagues. To be more polite, we call people by their last name plus teacher. And sometimes we call someone by his or her full name plus teacher. This is the most respectful way and is appropriate only in formal situations.