One tries to analyze and solve the problem on one's own and realizes his inner self too. Firstly, take the conflicting parties into confidence by listening to their complaints. Try to judge the situation and facts. Put the facts in front of them. Convince the person about his mistake in a sincere and sweet manner.
Counseling is the best method to convince people and rectify the situation.
If giving him enough time to rectify the situation does not solve it, use order. If that is no use, tell him again about the consequences of the disciplinary action. Give him a chance to rectify his error and try to convince him once again. Eventually, take corrective action.