How can a firm deliver after-sales customer service in an efficient manner?

I recommend to close the Quality Service Circle.  Contact your client by email or phone and thank him for the opportunity he gave you and ask if there is any recommendation or suggestion to make him fill better next visit.

Firm should treat the customer in the same manner in which they approached the customer to make him/her their customer. Should help the customer when every he/she calls.

the feed back is the most important point .. first you have to collect a good information about the customers satisfaction from many sources then you design your after sales services