Best thing what you can do is to learn a little bit of Korean in advance, because most of the people don’t speak English or there English is really bad that you don’t understand a thing. Prepare you for the same weather than in Europe. Don’t think that South Korea is on the sea you have the same climate as Portugal or Spain. Pack in warm cloths and take useless stuff with you because you can have it in Korea for a lesser price as sheets and clothes. The things what you have to take with you are towels, because in Korea they are to small and take a deo with you too, in Korea is hard to find or don’t exist. For all the other things your buddy can help you.