I'd like to pose a challenge. When was the last time you contacted your previous customers?
Not only is it good to contact previous customers for the references and testimonials they may provide, but there is also an opportunity for them to help you gain more business. The old customer has additional business for you either through how they've grown their business, or through the new network they can connect you with.
Some great questions to ask are:
"What other benefits did you receive from the product/service?"
"Who else do you know that would also benefit from the use of this product or service?"
There are also opportunities to up-sell. If the customer was pleased with the product you sold them, they are more willing to hear about the new products and services you have to offer.
Be willing to contact your previous customers on a regular basis, every 6-months to a year. Don't be shy that they don't remember you, they definitely will. And more likely than not they will be willing to have a coffee or an updated meet-and-greet with you.
Do you have an example of a previous customer meeting with you that led to more business?
What are some other reasons a previous customer would want to meet with you?