It seems to me that if you are speaking of a perception of ethical behavior outside your own behavior, then the greatest influence on how you perceive others' ethical behavior is whether or not it causes harm and the nature of the harm it causes.

For example, in an office place, an emotional breakdown with yelling and physical outbursts would be perceived far more severly because of the harm it does others than would the boss explaining why a report had to be reassigned because of inadequate work. The harm caused by the second (assuming the boss acted in a compassionate though firm and professional manner) would be seen as unavoidable because of some inadequate act, thus the boss would be perceived as ethical while the harm caused by the other would be perceived as unacceptable and even inexplicable thus wholly unethical.

If you mean how you perceive your own behavior, the greatest influence on that might be how others react and respond to your behavior. If others respond well and favorably in a difficult situation, then you might perceive your behavior as ethical while unethical if the response is adverse or unfavorable. Though of course there are always weaknesses to making judgements based on influences.

The ideas presented in the second post regarding consistent enforcement seem compelling to me, along with the ideas from the third post regarding models of behavior. Ethics, slightly different from morality, can be seen as a body of professional rules of conduct.

Ethics:

the rules of conduct recognized in respect to a particular classof human actions or a particular group, culture, etc.: medical ethics; Christian ethics.

Where morality is inclusive and applies broadly as a "social glue", ethics can be seen more exclusively, making the process of "learning ethics" one that is more likely to be learned on the job, in the work place, or from visible examples of specific group behavior. 

The most important influences on an individual's perception of ethical behaviors are his/her parents and teachers because it is essentially the job of parents and teachers to educate people during their formative years.

While those influences are the most important, every individual is also influenced by other people in the individual's local/national community and culture. This is clearly good and bad; i.e., certain celebrities or politicians are good role models, some are not. This is why I'd agree that a person's family and teachers (the education system) are the most important influences in establishing perceptions of ethical behaviors.

However, when an individual becomes an adult, it becomes his/her responsibility to compare those established perceptions of ethical behavior with what he/she encounters and learns as an adult.

I would suggest that an individual's own ethics influence his or her perception of another's ethical behavior. For example, I have a very hard time with youth acting with disrespect. Since I have insured that my own children act with respect, when I see others acting disrespectfully, it really angers me. While I know that this is the influence of the family, it was my choice to continue acting with respect (for everyone).

I would say that it is what a person's family thinks.   As we grow up, we are socialized more by our family than by anyone else.  Many of our attitudes about how to act ethically and about what things we think are ethical come from what our families teach us.

I think the biggest influence on what people think is appropriate behavior is what other people are doing.  No matter what influences have been in their lives, people will often act in accordance with what they see other people doing. There is often a case of seeing what other’s do and thinking, “why can’t I do that?”

This is an interesting question because it inquires about perception, rather than about reality.  I am assuming because of its topic that you are inquiring about the perception of ethics in the workplace.  I would have to say one of the strongest factors that affects our perception of ethics in the business world is that of consistency.  If we perceive that there is inconsistency in the enforcement of unethical behavior, we tend to feel as though there is no point in being ethical at all.  (That probably sounds dreadful, but it does reflect many people's thoughts.)  If I perceive that people are behaving in an unethical manner and there are consequences for some and not for others, I am likely to be far less motivated to behave ethically.  This kind of thinking ranges over the entire panoply of work behavior, everything from stealing paper clips to the misappropriation of funds.  Certainly, there are many other factors, but I see this one as quite important.