All the expat folks are going berserk over this, so I'm going to go over this as well.
1. Learn to drink like a fish
Sure, as I have said and posted in this blog, drinking is a big part of living in Korea. But! Do not confuse drinking being a big part of Korean culture and all Koreans being raging alcoholics.
Drinking is a big part of Korean life, yes. But plenty of people don't drink or drink moderately. I have been in American college, and I was in a all-Caucasian (except me, obviously) fraternity. Don't make it sound like Koreans are the only people in the world that drink lots. Drinking culture in Korea is deep and sophisticated, added with all the Anju and over a long time of drinking.
Don't make it sound like all Korean folks drink like douchey frat kids, partying and screwing.
2. Try not to get celebrified
Korea is a pretty homogeneous nation, demographically. Sure, some people probably haven't seen a white person in their entire life. Being a minority in Korea, especially if you've got white skin and blonde hair, might bring you a certain kind of attention.
This certainly doesn't give you the right to do whatever the hell you want (like that incident of playing cards and loitering in a subway train). Don't be a douche.
3. Bring your own clothing
Either you're ridiculously obese or you still haven't heard about the internet. Go do a simple search and you'll find plenty of stores and services for your size. Tall people, big people with big feet live in Korea too.
4. Learn to dance K-pop
Like this is all Korean people do, yeah right.
5. Put the Gay away
Certainly, Korea used to have a very strict and negative anti-gay sentiment. Not so much anymore. There are LGBT pride parades, LGBT clubs, LGBT organizations in Korea, especially Seoul. Look it up.
6. Buy good face cream
I think your skin is just terrible. Or maybe it's just your physical body being on the other side of the globe and experiencing a different climate? It's natural. You're thousands of miles away from the US. Obviously your skim might get rough if it's sensitive.
Also, face cream and cosmetics are popular in Korea... really popular. It's not because the weather and environment are terrible. It's just a trend.
7. Embrace your inner diva
Okay, I'll give you that. But nobody forces you to sing Korean songs.
8. Don't tip
Tipping is just a western culture. Tipping doesn't exist in Korea.
9. Don't have coffee addiction
Obviously you've never had Dabang Coffee(다방 커피). Real strong, real sugary. There are plenty and plenty of good coffee places in Korea. True, coffee is still a bit more expensive in Korea. Ever thought Starbucks was overpriced? I thought again in Korea.
10. Take pictures of your food
Yes, because people ONLY do this in Korea.
11. Adjust your diet
Nowdays everything in the US is in Korea. I only wish In'N'Out was here...
Go do some internet search, you can find about anything you can think of, especially around Itaewon. Also, you're in a whole different country, what did you expect?
12. Strike an Asian pose
Just don't. No. Just don't.