Another tip on avoiding fatal ethics mistakes:
Respect your innate sense of right and wrong. When we do something wrong, we often ignore an uneasiness about the action that we may not be able to explain. In a world of ethical relativism, it is unfashionable to claim to have an inner sense of right and wrong. And yet we do. In almost every fatal ethics mistake I have observed, the individual making the mistake sensed that the action was wrong beforehand.
In my book Make an Ethical Difference I explain what this innate sense of right and wrong is and when it should be trusted.