Our firm does extensive work in retail consulting and employee education (not "training"). We have found that most retail sales people or sales service people (those on the floor versus those behind the register), have been getting a bum rap. The complete responsibility for this lack of etiquette lies not with the staff but with the managers. Most often, we find two types of managers:
Those who were not taught to say "thank you," "excuse me" or "I'm sorry" and, therefore, never taught the staff. The second group of managers were taught these things but assume that everyone else was taught them too and so never educate the staff.
In the overwhelming majority of cases, the staff will do or say exactly what you want if you tell them exactly what you want. Typically, a manager may say "Be nice to customers" when he or she really should be saying "I want you to greet every customer with, 'Hello, I'm Russell, welcome to the Poster Store.' "
To most of us, this sounds foolish. No one ever had to tell us these things. It is precisely this attitude, however, that gets stores into trouble.