Make sure to get your fill of Kimchi. And stay away from fans in closed rooms, they are deadly there! (if you dont know what I mean, ask about fan-death).
Don't be afraid to go down side streets for food. Don't worry about not being able to read anything. If you're caucasian, the older generation of koreans will love you and will make sure to feed you the right things. Plus, the street carts have amazing food.