There is a big difference between mediocre customer service and excellent customer service and you probably have experienced an example of both kinds at least once in your life.
Mediocre customer service is often provided by employees who do not like their jobs much or at all; who feel they are unappreciated and underpaid; who think that the customer is somehow to blame for their low compensation levels, or maybe are just looking for someone to vent their rage at; or who were not properly trained in their jobs in the first place.
Excellent customer service is that great type of customer service provided by employees who are truly motivated to serve the customer the right way. You know you are getting excellent customer service if the employee serving you tries to give you the right product or service for your needs; when the way they talk to you is polite without being patronizing; when the employees go the extra mile to tell you what your options are as a customer; and when you overpay them and they return your exact change without being asked.
How does an employer manage to train employees to provide excellent customer service? Well, adequate compensation has always been found to be a good motivator, including perks like bonuses and benefits like health care. A happy employee is one who knows that he should serve the customer well so business will continue.
But excellent customer service also has a lot to do with hiring practices. As an employer you should be cautious about mass hiring and be more scrupulous at examining your standards for employees. This is why the Personnel Department often has an in-house psychologist who can spot potential troublemakers and weed them out from employees who have the potential for learning how to provide excellent customer service with the right training and guidance.