Customer Service is a delicate matter, needs to be handled with utmost care. Every customer is a unique in itself. Special personalized attention is required for each customer. All of your customers needs equal amount of attention. It is you who needs to do prioritization based on their need not importance in your business.
In the field of Customer services, After spending 12+ years of my career and still continuing with it, I have learned and practiced following philosophies:
Service is the right of every customer and it is your duty to extend best service as a customer service executive.
Customer is taking service from you with a very important assumption that you are the expert in the area of service you are offering. It is you who has to prove that assumption correct while delivering the service. Quality of service should be such that customer remembers only your reference when talking about the specific service of your experties.
Once you demonstrated your caliber for the subject matter of your service area, ypur customer will always fall back to you and spread your name to the broader community.
Key fact you have to remember always is that "You are actually serving yourself, while serving your customers and their needs are actually your needs and you understand them in a right view point and with perfact sprit."
"Change is Life. Non-Living can't change." --- A thought
"All people I know are superior to me in some kind of way. Because of it, I have been able to learn from all of them." - Ralph W. Emerson
Customer is always right, just try understand the correct context. --- A thought