''Ability to Read Customers''

This skill is self explanatory. The phrase suggests that as a customer service person,you should have the abilities read the countenance, mood or temperament of your customers at every point of service, as this will enable you serve them better!
You won't always be able to see customers face-to-face, and in many instances (nowadays) you won't even hear a customer's voice!
That doesn't exempt you from understanding some basic principles of behavioral psychology and being able to "read" the customer's current emotional state.
This is an important part of the personalization process as well, because it takes knowing your customers to create a personal experience for them.
More importantly though, this skill is essential because you don't want to mis-read a customer and end up losing them due to confusion and miscommunication (Gregory Ciotti).

  
While approaching a customer you want to serve(be it a first time customer or an existing one), look and listen for clues that will suggest their mood/current state of mind. Also watch out for their personalities, purported patience/irritability levels, as this would also aid in how you commence 'serving' them. Every customer service person/organisation MUST imbibe the psychological skills required to profile customers, this would go a long way in preventing possible discomfort and complaints by the customer, and thus create an excellent customer service image for any brand.