Nearly every sale has a repeat potential. It is not only easier, but also more cost-effective to market to an audience who has already done business with you (hopefully their experience was positive). Not only are they familiar with you and your business, but they have already shown interest in your products or services.
In addition to repeat product sales, up-selling is a great way to target current customers. For example, "if you like XX product, you will love QQ." Customers who are educated about their purchases feel more confident making informed decisions and will view you as the expert. Avoid being pushy, or you will drive away your current customer base. Instead, offer a lucrative discount that will do the selling for you.
In addition to increasing sales volume, current customers are also a potential goldmine when it comes to referrals. Customer referrals will not only help you build stronger relationships with your current customers, but will also help you expand your customer base through increased awareness to prime prospects.
There are many ways to generate customer referrals, but one of the easiest occurs throughout day-to-day conversations. If a loyal customer compliments your business in casual conversation, ask if you can use that statement as a customer quote.
Repeat customers offer stability and predictability -- a must for any successful business. After all, happy customers can sell your business just as well as your sales team.