What sources have helped shape your personal code of ethics

What sources have helped shape your personal code of ethics and morality?  Think of an experience you had at work or school that tested your ethical standards.   How did you resolve your dilemma?   How that time has passed, are you comfortable with the decision you made? If not, what would you do differently?   

Solution

When, I was in school my friends were smoker. They smoke during the class session. It disturbs and effects bad on other students. I was in ethical dilemma; I did not want to report my principal about them. But getting right approach and saying the truth I had reported this issue to my principal.