Post-Order Customer-Support Issues
The author also identifies two obvious support issues after the purchase: order tracking and problem resolution.
It should be possible for you to tell the customer, at every step along the way, where the items he ordered are, and to provide a package code to enable them to monitor third-party delivery services who handle their goods.
Also, not all sales go smoothly, and a key to retaining the future business of a customer is responding well when a crisis arises. There will be problems filling the order (no inventory, shipped wrong, etc.), damaged or broken goods, etc. and you must handle these processes elegantly (and to the complete satisfaction of the customer).
Beyond the support issues, you can also re-contact the customer after a sale to ask for their feedback, or market them for future purchases