Your conscience is one way for you to judge wrongdoing from a simple mistake. Your conscience leads you to a sense of feeling guilty when you do wrong compared to simply being imperfect in making a mistake. Also, think of your intent in what you did. Did you deliberately decide to go against your own standards or not? If you intended to do wrong, and then acted on that desire, then you engaged in wrongdoing.
Another area is the action itself. Some actions are wrong in and of themselves, such as disrespecting another person. So, conscience, intention, and action all can help you decide if you have done wrong. One area that is not as straightforward is the other’s reactions to you. Sometimes, for example, a person will be very angry with you and tell you that you did wrong. If, however, your conscience is not bothering you on those actions and if you truly did not intend to do wrong, then the other may be over-reacting.
For additional information, see What is Forgiveness?