You have answered your own question already. You have to be good in treatment of your customers. Because your customers that are satisfied by your product or service will refer you to their family and friends.getting a customer is very good but to retain the customer is another challenges. Your attitude towards your customers is so very important. Have you forgotten that a customer can refer so.many customers to you if you treated him/her very well likewise a customer can destroy your business, sending away your customers by telling them bad about you,if you don't treat him/her very well. So what and what can someone do to retain customer after you have made rigorous marketing?