Since you can’t always know a person’s age upon first meet, it’s better to err on the side of caution. Koreans differentiate between using two hands for a handshake vs. One hand can be used by someone of higher rank to someone of lower rank, but not vice versa! Though this is what we may be used to in the West, this is one mistake to avoid in Korea.
If you are trying to learn Korean, you can add this helpful word to your vocabulary flash cards: 노약자석 = seating reserved for the handicapped, the elderly, and pregnant women.
Many expats and visitors who are strong speakers of the language were able to learn Korean fast by spending lots of time with Koreans.