After 4 years of living and working here, without much of a vacation for a while, here's the low-down (as from what I have accumulated)
1. Live in Seoul. I say this because though some places reasonably close to Seoul are very nice, most everyone you meet will want to take a trip to Seoul almost every weekend (since that's where people go to party, both Foreigners and Koreans).
2. Learn Korean, at least some so you can get by. I STILL have friends who can't really speak it, or don't want to speak it. They've been here a good while too. The thing is, if someone is speaking in English while everyone else speaks in Korea, you tend to get a lot of glares from older people, and the occasional to frequent "be quiet" or "shhhh" as loud as they can to let you know that though they too are speaking loudly, they do not want to hear English. If you drop in some Korean now and then, they leave you alone. If you're around the working-class, this happens a lot.
3. People drink a lot here. If you enjoy drinking socially, you might be in for some major culture shock. Most people drink daily, starting around lunch time. If you see a group of older men, don't be surprised to see then pounding the soju at 12pm. A LOT of people tend to get wasted on a nightly basis. Either drinking with buddies, drinking with coworkers, to team drinking (which means big groups from businesses go out drinkin). Some business students I've had aren't too happy with doing that on a weekly basis. They might go out for a few drinks, but if they see their boss, they gotta drink themselves silly.
4. NEVER get into any sort of argument/fight with an 아쭈마. You just won't win. You will hear old people yelling a lot, but they're just being loud and animated. There are those of the younger generation that are starting to not show the loud, obnoxious older people little to no respect these days. They're becoming a little more "independent" but actually, theyre just not caring (or being lazy).
5. If you love kids, and I mean you love them like they're your own and can do no wrong, then work with them. If you like kids, don't work with them if they're under middle school/jr. high age. I've taught kinder-6th grade these past 4 years. I've never lost so much patience as when I've taught some of these kids. If you work in a poor area, they kids tend to be well-behaved. Rich kids tend to think they can walk all over you because chances are their parents raise them that way.
6. If you work in a hagwon, expect a lot of last minute announcements on a daily basis. generally, "hagwon managers" always think of something at the last minute (poor planning), and they dump it onto you "we need to get all of this done by next week" sort of thing. It'll constantly happen, so don't get stressed over it.
7. If you plan to stay here for more than a year, think about finding your own place. SOME schools will find you decent housing. Most will find you some place that might be underground, and next to a sewer line.
8. Though North Korea always does something to get attention, most Koreans generally don't care anymore. It's become second nature to them. But when something happens and it's "done" by a foreign teacher, some of those same people demand blood (journalism here is about as truthful as Milli Vanilli singing live back in the day).
Ok, that's some of the negatives...here's some of the positives:
1. generally, if you live in a city, things are very accessible, and very convenient. you can sometimes set your watch to the subway and bus system here.
2. most things are very inexpensive...unless it's imported or designer-grade material. Sometimes it's just an exchange rate conversion.
3. people are more health conscious these days. You will see more people going to gyms than you might expect back home, or even back in college.
4. Most of the friends you meet here will become closer with you than you are with your friends right now.
5. It's very hard to leave, even with all the negative things, it's very hard to do it (unless you come only to make money)
6. there are always teaching jobs available. If your job treats you horribly, then get a new one, don't worry about the visa stuff, just get a letter of release from where you work and take it to immigration along with the new contract.
7. learn korean, and you will not only make native korean friends, but you will also make very good connections down the road, and in this country, it's not really about what you can do, but who you know, or what circles you are involved with.
I got a feeling i've said this before....but this time it's 4 years instead of 2 (or whatever)
oh yeah, recruiters will try and give you horrid jobs, so if you go through them and don't search, you will wind up at some place that treats you like a slave. I recommend
English Spectrum and
Work n Play(Dave's isnt that good anymore)
Good luck, Happy hunting, and above all.....just play it cool