Anyone can ask “how was your weekend?” The second question is where people realize you actually care.

Anyone can perform interest once. The first question is a social move that costs nothing and gets an answer built to be easy; the second one shows you listened to that answer instead of waiting for your turn. That is where people decide whether you meant it. Following up is the whole difference between politeness and attention.

Take whatever they said and ask about one detail inside it. Use their words rather than yours. Do it twice and you will end up in a real conversation, which is more than most people get in a day.