Learn the language. It may seem daunting at first, but it is very easy. I learned to read/write/speak Hangul (Korean) without any formal training in the short time I was there.

There our many strange customs you will discover. Most of them will not get you in touch much trouble if you violate them. Koreans are understanding people and will realize you don’t know their customs.

One strange custom I can note off the top off my head is this; if you go out to eat pizza (they have several Pizza Huts in Seoul), it is considered rude to eat pizza with your hands. You must use a knife and fork.

Another custom that you might find strange is that if you go to a barber shop, the haircut almost always includes a massage. If you refuse the massage it may offend the barber.

I recommend the book “Learning to Think Korean” by L. Robert Kohls. It’s an excellent book that takes you through many every day kinds of situations that often baffle westerners. One thing to keep in mind is Korea (and most of Asia) is a much more hierarchical society. There is more formality between teachers and students, bosses and subordinates, even between parents and children. Many of the problems westerners encounter is due to not understanding the expectations that “superiors” have of subordinates and visa versa.

One tip as a teacher. Asian classrooms tend to be much less participatory than western classrooms. Students tend to just listen to lectures and memorize information. I think it can be still beneficial to introduce some of our methods of teaching into the classroom, but just be aware that you are going against the grain, and it may take a bit of cultural sensitivity and patience to get good classroom participation going.

Hello!
It has been some years since I’ve been to Korea, but if possible, do try and get some info on the customs of Koreans. If you will be teaching, the kids over there are about learning; I believe they go to school like six, seven days a week there. Their national food is the kimchi which is cabbage with spices that have been fermented for some time and eaten usually with a meat or another vegetable; Shopping in Seoul in Itaewon is the place to go and you can get great bargains there. For now that is all I can remember, but keep in touch. And the best to you.

I highly recommend you read the following book:
The Koreans: Who They Are, What They Want, Where Their Future Lies (Paperback)
by Michael Breen

It has been a great asset in my travels to Korea.

Hmm I remember a friend of mine who said never touch Korean children on the head. I never saw that one in person though.

2 customs relating to eating I remember from being there – Never pour your own drink if eating in a semi formal situation. Always let someone else pour for you, and to be polite, you should pour for them.

Also, when pouring and when holding a cup for someone pouring for you, there is a distinct way to hold the cup and how to hold the bottle. The first time you go to dinner you’ll see and then you can duplicate it.

Sneezing without covering your mouth, bumping into people while walking on the street, parking and driving cars on the sidewalk, getting drunk and fighting, staring at foreigners, nonsensically hating American products, hating Japanese people, talking really loudly and eating kimchi for every single meal and snack are the main ones.

I’ll second Muddart’s idea. I highly recommend the book Learning to Think Korean (check out a description at http://www.amazon.com/Learning-Think-Korean-Working-Interact/dp/1877864870/ref=sr_1_2?ie=UTF8&s=books&qid=1249308123&sr=8-2). It has all sorts of stuff about customs and avoiding social faux pas that are REALLY helpful. You can get it on half.com or other used book sites. Also, Culture Shock! Korea is really good for this kind of stuff.

As several other people have suggested, I would also try to learn at least a little bit of the language. Around Seoul many people (especially younger people) speak English, but showing that you care enough to try to learn their language but just making that effort goes a long way in terms of establishing good will with anyone you come into contact with (as does trying different Korean foods).

But off the top of my head:
1. You don’t pour your own drinks when you’re out with people. They fill your glass and when you see their glass getting low/empty, you should offer to fill theirs.
2. Cover your mouth when you use a toothpick.
3. Whatever you do NEVER stick your chopsticks in a bowl of rice (meaning stabbing them into the rick so they’re sticking out perpendicularly). That’s something reserved for the dead.
4. Koreans, unlike other Asians, eat their rice with a spoon. This isn’t so much a “you’ll get in trouble” issue as a tip to fit in better.
5. If you have any dietary restriction, DEFINITELY learn the phrases to express them in Korean ASAP. I’m a vegetarian so I had a lot of issues (Korea is not a very veg-friendly country).
6. If you’re invited to someone’s house, it is customary bring a small gift (doesn’t have to be expensive, just something to express your appreciation for your host/ess’ hospitality). I’d suggest bringing things from America that would not be available in Korea because people seem to like that a lot. And in Korea, traditionally people don’t open gifts in front of the giver so don’t be put off if they tuck it away for later. As a teacher and foreigner, I would not be surprised if you get many invitations to people’s houses so be prepared!
7. Probably goes without saying, but take your shoes off when you enter your house or anyone else’s.
8. You may want to be aware that it is very common for friends of the same sex to hold hands in public. It doesn’t mean they’re “a couple.”
9. When you go out with Koreans, you do NOT go Dutch. One person pays and, although I’ve never experienced it, I hear there is sometimes a big “fight” (i.e. friendly arguing) about who gets to pay the bill. You may want to read more about this but basically it’s an “honor” to pay the bill and shows your generosity and stuff. If you’re the oldest member of the group it may be more likely that you’ll pay (though I’m not sure if that changes since you’re a foreigner), but if do go out with the same group of people several times, make sure you take your turn to pay. You may have to “fight” for it, but it is appropriate.

Well, I guess I remember more than I thought. Hope this helps!

In addition to the great advice other people have shared here already, there are a lot of great perspectives and suggestions here: http://forums.eslcafe.com/korea/

When I was living and teaching in Korea, that forum proved invaluable.

I also recommend learning to read and write Hangul before you even depart for Korea. It is easy and fun to learn and makes getting around via bus, etc… so much easier (not to mention reading food packages, menus, etc…). Also, it will really impress your students when you can write their language :)

I hope you have a fantastic adventure living in Korea! I know for me it was really incredible. Good luck!