In simple terms, ethical behaviour is knowing and doing what is right. Which can be implemented naturally by building a strong sense of moral. Trustworthiness, truthfulness, lawfulness, honesty, responsible, sincere some of the many fundamentals of behaving in ethical way. 

To behave in ethical way a person needs to have a pure purpose and straight forward approach to any situation. This makes leading a ethical life much simpler. 

Strong sense of ethics are not developed overnight. It takes time and will. We learn our sense of ethics from our surrounding situations and people. So choosing the right people can be helpful.