Customer derives from "custom," meaning "habit"; a customer was someone who frequented a particular shop, who made it a habit to purchase goods of the sort the shop sold there rather than elsewhere, and with whom the shopkeeper had to maintain a relationship to keep his or her "custom," meaning expected purchases in the future.
Because today customers will not go back to being anonymous masses you can market at, and because as a company you may not have the luxury of such a fat marketing budget any more, you need to invest in the right kind of tools that will put the information at your fingertips, when you need it.
While typical customers don't exist anymore - we've all become individuals, especially thanks to online access - there are now more ways to learn about who your customers are and what they want and do. If you invest time and attention in capturing the data and doing something with it (the doing part is especially important).
So listening is the first priority to engage with customers