This is a great question. In light of all the corporate scandals and the world of "creative" accounting practices, we need some clear leadership in the area of ethics. With this said, I love how you ask your question, because it assumes that actions and structures must be in place. I totally agree; people cannot be left alone to do the right thing. The temptation is too great. In light of this, I have a few suggestions.
First, there must be accountability. So, decisions should be made jointly. To incorporate other people creates accountability. In addition, these decisions should be checked over through an internal department - perhaps internal accounting.
Second, there should be greater transparency. In other words, facts and figures should be divulged to shareholders and the public. In this way, there is another level of accountability through transparency.
Finally, there should be a handbook of corporate ethics and a department that investigates these matters. If these steps are taken, it will help.