Generally subway stations in Korea are very clean and convenient. Somehow people do behave in keeping orders. Subway trains are in most cases punctual and they run very smoothly without much trouble.
You can see signs in Korea, Chinese and English. Announcements that give you information on the next stop, to which line you can transfer in the next stop, etc. are in Korean, Japanese, English and Chinese. This can vary a bit according to which line of subway you are using.
Everything is well maintained and it is almost spotless. Cleaning ladies keep these subway stations really clean. Every station has a clean toilet as well.
You can often see short-run stores. They show up for a few weeks and months and they move to a new place in many cases. You can find clothing store and shoe store as you can see from the above photo.
You can often buy coffee, waffles, manju (Korean snack), Gimbap and more in case you are hungry. They are not so expensive ranging from 1,000 won to 3,000 won or so. Many people would not like it when they find out that you are eating food on the train especially if they are a little smelly.