A couple ways to increase service and quality are to not make things worse for customers.
This would include helping them check out merchandise. If you disagree compare a grocery store with baggers to one with self bagging. Another comparison is at nice hotels do you take the bag to your room, or does a bell hop?
Another is not to annoy guests with noise and inconvinience. If you disagree think of when you bought a CD or somthing and the security tag wasn't inactivated or removed, and even though you paid you had to go back in and everyone else had to hear the alarm.