The most common mistake is to put profits first. That opens the door for bad things to happen. Numbers become all-important, and almost any behavior is justified in the name of profit. Cheating sets in.
Instead, a company's priority should be to protect and enhance its reputation through ethical behavior. Within the confines of that behavior, its next most important goal should be to attract and keep customers. Third is figuring out how to make money.
It reminds me of http://www.itsnotwhatyousell.com/pdf/ch1-spence.pdf