The following information has been taken from The Essential Guide to Customs & Culture: Korea.
I have been pretty nervous about not knowing all of the behavioral differences between Western and Eastern cultures. It is in these subtleties that I will find my success or failure with my students and new acquaintances, so I of course have skimmed this book at least once. Here are a few of the more entertaining differences from the 100 pages I have highlighted in this book so far.
-It is traditional for those seated on a bus or other form of public transportation to hold the bags of standing passengers. One should not be surprised if a heavy bag is quietly taken from them on a bus or train. It is not a thief but a seated passenger hoping to relieve you of your burden for the duration of the ride.
-Some Korean women will smoke and drink (especially if they are over 60) (SIXTY?!) lead independent lives, and file for divorce. A growing number manage or own businesses. Women are well represented in many professions. There is also a strong feminist movement in South Korea.
-Many Koreans avoid the number 4 (sa) since it has the same pronunciation as the word for death. Thus you will often find that some Korean buildings will not have a fourth floor, or that the letter "F" replaces the number. Because many Koreans are aware of Western superstitions, the number 13 may also be missing.
-To use the left hand is seen by all Koreans as offensive. It is best to offer something to another person, especially if they are senior in age or rank to you, with both hands. If that is not possible, use the right hand.
-Do not stick chopsticks upright in rice as this resembles the way incense is burned at funerals.
-Bare feet are generally to be avoided. (WHOOO! I hate feet. Could not be more ok with this.) Koreans live eat and sleep on the floor, so it is important that floors are spotlessly clean. (The author notes: I have been reprimanded for not wearing socks with sandals by a total stranger on the streets of Seoul.)
-Gold is the best color for wrapping gifts, and all gifts should be wrapped. Avoid black and white.
-Displays of bad temper are regarded as the height of bad manners and are unlikely to achieve much. It is also best to avoid direct criticism as far as possible. If you have to criticize, do it in a vague and roundabout way, and do not do it in public. The direct approach will leave your audience embarrassed and uncooperative.
-Koreans may slurp soup, burp after a meal, and clear their throats noisily, but they do not blow their noses in public.