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. Also, whenever I take something from another person, I usually use both hands, either gripping the item with both of my hands, or using one hand to support my other hand.
Honor and respect are important in Korean culture and in Korea's community. Korea is a very hierarchical society, which means that your status determines how you are treated. Koreans are known to ask very curious questions in introductions because knowing another person's age, job or marital status can help determine how you should speak and act around that person.
