Database Marketing and contact with that customer database.
How often do you follow up with your customers that have bought from you? What about those potential clients that have not bought from you yet? Is there structure? Back end sales to current customers? Do you have a marketing system for generating referral business and additional sales?
These are crucial to growth in a business. Lacking in this area will mean that you constantly have to source new customers to make money in your business and that process is getting more and more expensive as we continue.