After my 2 week trip to South Korea, here is what I learned and used. I hope this will help you with your trip to South Korea. One more thing, try to pack light if you plan to shop.
Traveling to and from Seoul
Airport: There are 2 International airports near Seoul. Inchon International Airport a little further from Seoul but is now the main International Airport (this is the airport I arrived at from California). Gimpo International Airport is closest to the city and is considered the old international airport which now mainly serves domestic flights and flights to China and Japan (We flew to Jeju Island from this airport).
Bus: We also made a trip to Daejeon, South Korea; the 5th largest city in South Korea for a friends wedding. My friend recommended that we take the bus because it was the cheapest option.
Things to do before leaving the airport
Exchange Money: I personally think it is easiest to exchange money at the airport, the exchange rates were fair and I don’t remember having to pay any other fees.
Get your Cellphone working in South Korea: It’s not cheap (and probably won’t get the best connection) to use your own cellphone on its own network in a foreign country. I highly recommend renting a wireless router for your smart phone. This way you can access apps, maps, search for information, and communicate with friends and family. Just make sure you keep your phone on flight mode the whole time.
There are several major companies that provide this service. I went with SK Communications. The unit we rented allowed us to connect up to 3 devices and up to 500mb of data per day. You may also want to get yourself a portable charger just in case your wireless router runs out of battery.
My only con with just getting a wireless was that we couldn’t make any local calls. And we were not able to contact any friends who did not have a smart phone (which seems odd in South Korea, but it really did happen to us!). I would have also rented a (not so smart) phone for that.
Get a T-Money Card: I used my T-money card everyday to get around. You can get one at any convenient store. 3,000KRW for the card, and just add as much money onto the card as you like. You can also use this card in Daejeon and at any convenient store as well. Just let the sales clerk know that you will use your T-money card and place the card on the scanner (usually attached to the credit card sign box thing).
I ended up getting a cell phone case with cover and and a card slot for my T-money card. Each time I used the subway, I simply took out my phone instead of pulling out my wallet and then pulling out my T-money card.
Traveling within Seoul
Subway: The easiest way to get around Seoul is via the subway. I have listed the subway line, station, and exit for most places I have been. I would recommend downloading an app to help you navigate the Seoul subway system. The subway will also take you to the airport.
Apps I used the most
Jihachul Subway App: I used this app to get everywhere. I simply chose the subway station I was departing from and planning arrive at. From there it told me if I needed to make any line transfers (which were not always fun), how much is was going to cost, and the approximate times the subway train will arrive at. I was also able to pull up a quick map of the subway station and its exits. (available on android and iOS)
KakaoTalk: I have always used this app to chat with friends in South Korea, but I had also found that it was a great way to communicate with my family at home as well. All I needed to do was make sure they had KakaoTalk downloaded on their phone or tablet. You can also easily call them using this app. You can also use any similar app. (available on android and iOS)