It's been a while since I was there but as a lowly US Army Private stationed there and working closely with Koreans old and young as an ambulance driver, there are a few things I still remember clearly.
Basic courtesy and being polite are pretty much universal, so try to be humble and keep an open mind and observe. Older people often are more experienced and savvy about how to handle something so being deferential to them is a no-brainer. You'll spot the incompetent ones soon enough and so continue being polite but ignoring their guidance.
One thing that drove me nuts but took a little while to figure out was that people would almost never say no to a request. I would ask if something was possible and they would pretty much always say yes, not wanting to disappoint, but I would have been better off hearing a 'no, sorry'. I wanted a realistic answer and theirs were often far too optimistic.
Me: "Mr Son, can we make it to Osan in 30 minutes?"
Him: "Yes" (always yes)
An hour later we show up late to another hospital with a very impatient air crew idling and waiting for our patient transfer. We would have all been better off hearing a "No, it takes an hour". Just one small example but this scenario repeated frequently.
I learned that when speaking to a group or doing a presentation it was customary to apologize for your inexperience on the subject and promise to do your best. Tim Berners-Lee could start a talk with "I'm sorry I don't know much about the World Wide Web..." for example and Westerners would laugh but the locals would be like "He's off to a good start".
Understanding this helped me get more realistic answers though. Even if I thought I knew an answer I would keep the question more open-ended to solicit a better response.
Me: "Mr Son, I'm sorry but I forget how long it takes to get to Osan, can you remember?" (said even after making the trip solo dozens of times in often difficult and stressful conditions).
Him: "Ah yes, there is new road construction halfway there so I'll teach you an alternate route to bypass it. We'll be there in about 40 minutes".
Had I not learned to ask a better question, I never would have learned his faster alternate route.
Korea was a lot of fun and I really enjoyed hanging out with the older Koreans who worked on our base, they were a constant source of good info once learned how to talk to them. I also had a 'ration card' entitling me to buy the occasional bottle of Crown Royal on base and give them, which always helped!