Having gone to the expense of acquiring a new customer, think about ways you can do more business with them. It is much cheaper to sell to an existing customer.
Do you have a product of services that goes with what they have just bought from you.
Do a follow-up with the customer, invite them to friend you on Facebook. Let them know about any discounts or incentives you offer for referrals.
Wikipedia has some great some background reading on Customer Lifetime Value.
As always, if you have any questions or comments, please do let me know. I would be happy to help.