You thank the customer and that's it. Reacurring sales are from previous customers so, the best way to show your appreciation is to ask your customer for their birth date and anniversary. If applicable ask for their children's birthday as well as the spouse. Send birthday cards, anniversary cards and holiday cards. This is a sure way for your customers to remember you and your business.
People love sincerity with a smile.
They're also more likely to refer you to a friend and or family member. Practice makes perfect. People don't plan to fail. They just fail to plan. If you don't aim for what you want to accomplish, you won't get there.