What advice would you give to someone going to Korea (first duty station) who has never been out of the country before?

Katusa are your friends, especially if you are stationed in Seoul. Tell them that you will spring for dinner and have them show you around town. Who best to show you Korea, than another Korean.

Maj John Bell remarks are spot on. Should be briefed to anyone going overseas at least 1st time.
My wife is a South Korean, yes there have been rough spots (as there are in all marriages), but thanks be to God we have worked through them. 38 years in October.

Never go into town by your self, at least 2 or 3 buddies for about 6 months. Look like you have been there before because the locals can spot a newbie before you step out the gate and will take advantage of you before you realized you where scammed. There are a lot of do's but a bunch more don'ts. Find a Battle Dad that's been there before. Oh! every service member has the same name. Either G.I. Joe or Joe, so don't be offended. Don't be dumb, stupid or overly smart. Just use basic common sense and you will be fine. Good luck and best wishes.

Know your limits on alcohol. Korea is one of the easiest places to get in trouble when it comes to alcohol. You'll also work with KATUSA soldiers. Become friends with them, and get them to help you learn the language and culture. Some of my best experiences in Korea were hanging out with my KATUSAs on the weekends. They took me places that MWR would never schedule. I still keep up with a few to this day, and it was 2006 when I left the country.

Mainly, the best advice anyone can give you (other than not coming back with a wife) is to get out of the barracks and experience the country. You're going to be immersed in a new culture and it's one you'll love to be a part of. And if you're into sports jerseys, you can definitely get a bunch on the cheap there.

enjoy it!
learn the customs.
show respect(YOU are the foreigner)
get away from sailor/soldier town. most bases usually have tours/excursions for the country they're in. sign up for them. never know, you might just learn something!
don't get attached to the b-girls. yes they've had/have a hard life but...they want your money or they want the information you may have. for the 20 yrs i was in the navy, the b-girls always knew what ship was due in and when almost right down to the time.
find a good liberty buddy and stick with him/her

Birth control is a must-condoms!! But have fun!!!

Learn all that you can about the people and customs.

Once you've gotten established, travel and see the country. Between the subway app and KakaoTaxi, transportation is pretty easy to come across even without a POV. The people who hate being in Korea are the same dudes who are cooped up in the barracks every weekend. It's not the best posting, but it'll be what you make of it.

Korea is OK very westernized if you are adventurous about food there are lots of things to try. I was at Camp Humphreys it was OK. I know a couple of people that liked it so much they asked to stay there.

Stay away from the so-juw. Do not have sex with any Bar Girls. KEEP EVERY THING LOCKED UP. The rest deponds on witch base of Camp you go to. If you are lucky enough to go to Camp red cloud or farthe south. Life will be Good. Every thing is better.
There are lots of thing to do that will not get you into trouble, unless you are a Dumbass.
There are all Classes to take at Camp Cassy and farter south. I was at Gerry Owen. Dec-1999-Dec-2000. All we had was a pool that was always nasty, A N.C.O. Club that sucked.
Then out side There was the choice of Bare's that ether had Russian or Phippenio bar girs with over priced beer and the girls. Let me tell you about the Girls ( Being one of the medic's ) Most of them I knew of gave a lot of the guys more than they paid for. If you get my meaning.
Most of the lacals that I delt with where good people.

If you can learn to speak Hangeul. A lot of American's go to Korea then get butt hurt because most Koreans do not speak English. Do not get me wrong I would have liked to go back to Korea there are lots of things to do if you are at the right duty station. Try to find out the places that your M.O.S. Is located. this can help you find out what life be for the most part. along with the enducation opportuntys.
If you are married depending on duty station you may get a two year and bring them to korea.