Common sense is a form of practical decision-making and the ability to imagine the consequences of something you do. It stops us making irrational mistakes and makes it easier to make choices on what to do. We aren't born with common sense, we develop it over time. Although common sense can come naturally to some people, it can also be harder for others. Sometimes, you may not even realise you're using it, as it just comes to you naturally when in certain situations. There is no direct answer as to how you learn common sense, because it is something that is developed over years.