Timely and smooth delivery
With much shopping nowadays being done online, it’s clear that in order to retain satisfied customers your business should provide a first-class delivery experience. The delivery of products should be fast, while giving the customer the opportunity to track the package and receive relevant updates at every stage of the process. Needless to say the delivered products should be in excellent condition.

Personalization
This is, perhaps, the key factor to retaining customers, since it makes them feel special. So you need to be original and innovative when deciding on a number of issues, from the delivery box to a potential gift accompanying the purchase.
Immediate follow up
As you know the date of delivery of the product or completion of the service provided, you’re advised to send an email or a message through which you express your thanks, reminding customers that you remain at their disposal for anything they need, both for the present or for any future purchases. It's a good idea to accompany this communication with coupons or offers.
Keeping in touch
Once your business has the customer's contact details at its disposal, then you can schedule sending emails with offers, special discounts or reward programs from time to time. In this way, communication and interest are kept alive. Note: The first few messages may not immediately translate into purchases. In gradually building a business relationship with your customers, time and constant monitoring are required for the communication to improve.
Utilization of social media
Many customers spend a lot of time on social media, so it’s advisable to post content –ideally the same one you used in your communication emails– in order to arouse the interest of your customers.
Clearly, customer retention is not easy, as it requires adaptability, with consumers' habits and desires constantly changing. The best customer for your business, however, is not the one who buys once, but the one who returns, recognizing your company's value. So that’s what you’re aiming for.
Sources: The Invesp