Apparently, the bumping into each other has a philosophical background. The Koreans are generally of a Confucian belief system. Part of Confucianism is respect for others. When you bump into a stranger on the subway, you don't know how to address them. Are they of higher or lower status? You don't know, not until a formal introduction is made by someone else. So apologizing for bumping into someone is actually more trouble than it's worth. You would have to find out where they work, what age they are -- anything having to do with their station. It's easier to ignore the brush of shoulders. Of course, if I body checked an old Korean woman, I would need to apologize!
This is part of the subway station at Yoeido Island (but during the cherry blossom festival, so it was unusually crowded)
Giving a business card to someone is a big deal. It determines the respect the other business person should have for you. The card is meant to be presented with some ceremony. After a formal introduction, the card should be handed over, at the very least, with the right hand. It is better to present things with both hands, especially for a business card. Most Koreans will receive things or hand things over with their right hand and hold the middle of their right forearm with their left hand. Giving something with the left hand is actually disrespectful. Most of this comes from a Korean guidebook, but now that I'm aware of this custom, I've actually noticed a lot of the respect shopkeepers give me with using their right hand.
Bowing when you say thank you is another sign of respect. This might be obvious for some, but when thanking someone, you should bow a little lower than them if they are older or deserving of more respect.
Many of the women walk around with a hand or paper to cover their face from the sun. I have a sneaking suspicion that this is because they prefer pale skin. There are many skin care products here meant for whitening skin. It could also be to prevent squint lines. The older women tend to wear giant visors that cover their entire face. They tilt it way down so you can't see their face, but they can see you.
This was at the Seoul Museum of History - probably doesn't apply anymore.
Between friends, sharing food from the same communal dish is a way that builds friendship. Many Korean restaurants will just serve the food on one big dish rather than on separate plates. They give you separate plates and it isn't considered disrespectful to move food from the communal dish to your own plate.
All very interesting.