One of the chapters in company of one, author talks about customer support.
Customer support and level of delight are what makes a brand stay out of the crowded competitors. He gives an example of Rackspace’s famous pizza story and Trader Joe’s.
Startups run after growth and getting new customers. They can apply various marketing approaches, discounts for the same. The major differentiator happens to be how they treat their existing customers. A 10$/m customer for 10 years period worth more than 100/m/y customer.
Treat your customers as you would like to be treated. Many companies like Trello, Basecamp got all their customers via word to mouth. They were able to achieve it by delighting their customers.