I would try to go directly to the source. Maybe engage with the child and try to understand, why are they misbehaving? Could it be for attention or love? Are they trying to make themselves feel better? These are difficult questions that he/she might not even know. Try to make the person see how their actions is impacting others but also themselves, ie: If he/she is being mean/rude, it will not only hurt someone's feelings but it will also make this person seem less approachable. As a result, they may have difficulty making new friends. Most actions have reasoning, only they can be difficult to understand. Try to help rather than reprimand and always encourage positive behaviours.