One way I can think of is by introducing a reward system. I'm not sure what your business is, but you could put something in place where each employee gets a bonus, or a voucher or something for every, say, 10 items they sell.
Targets and KPI's (Key Perfomance Indicators) really help. One of the best ways is too gain employee buy-in. Give them ownership of a project and they will want it to succeed not just because its their job. It also allows them to feel they have a worth within the company.