Elders are treated with high levels of respect by their kids, grandchildren, and even strangers on the street. They are usually served food first. Additionally, in certain situations, people that are younger have to turn their cups away from the elderly while drinking. There is also a higher form of speech when talking to the elderly. This honorific form of speech honors the elderly and is only used when talking to or about the elderly.
If someone is a year older or younger than you, it will affect the way you speak to them. When you are a little older than someone else, the younger person is supposed to show you respect. The younger person is supposed to call you older brother or sister and are expected to use more indirect phrases. If you are older you can use casual speech with the younger individual and use direct phrases.
When you speak to strangers, you have to use polite speech. Polite speech is a little less honorific than the speech used towards the elderly. It shows that you are a respectful person and honors the stranger as well. It would be rude to talk to a stranger the same way you talk to your friend.
Bowing is widely used in Korean culture. It can be used to say hello or goodbye. It can also be used when you are saying thank you or when you are recognizing someone's gesture. A typical "hello" bow is just a slight bend of the neck and shoulders. I have never seen anyone bow 45 degrees, but I hear that is still used in very formal settings.
Another custom I learned is that whenever you pay, you are supposed to use both hands. I was told that using both hands to hold the money is showing respect to the other person by being careful and courteous. I do this whenever I go to a restaurant or to the convenience store.
