This is a very important question. In view of all the corporate scandals, it is important to have a corporate culture of ethical behavior. In order to do this, there must be certain structures in place that will create accountability and certain checks and balances. Let me give you a few suggestions.
First, plurality is important. Decisions should not be make by one person. There should be accountability with others. And the more important the decision, the more this accountability is necessary.
Second, there should be an external accounting firm that looks over a companies records to make sure that all the finances are in order. Perhaps more importantly, this information should be divulged to the public. This will create great accountability and a check for corruption, because the company will have to answer to investors. In a word, we are talking about transparency.
Third, a company can empower members of the company to speak up against unethical behavior by setting up a department that takes these cases seriously. In fact, a handbook of ethical behaviors and disciplinary action would be a good start, so that all employees would know what is expected.