Originally Posted by
mikesaidyes
Go to the basement and try the jjimjilbang (Korean sauna) while you wait. Just really throw yourself into the Korean experience. There's free wifi throughout the airport (can't verify the basement jjimjilbang, though).
Otherwise, it's just a bunch of random cafes and restaurants. If you walk over to the train station building, you can ice skate and even go to CGV cinema.
Highly recommend the sauna. It is called Spa on Air down in B1 level. Even if to just take a hot shower. You can tell your friend to make his way there after arrival and then meet inside the lounge area.
Another easy place to meet would be the McDonalds on the arrival level. It is in the middle of the airport and hard to miss.