Effective follow-up begins immediately after the sale when you call the customer to say "thank you" and find out if he or she is pleased with your product or service. Beyond this, there are several effective ways you can follow up to ensure your business is always on the customer's mind.
For example, let customers know what you are doing for them. This can be in the form of a newsletter mailed to existing customers, or it can be more informal, such as a phone call. Whatever method you use, the key is to dramatically point out to customers the excellent service you are giving them.
Excerpted from Grow Your Business