Every person goes through several stages before becoming a buyer.
These stages are:
People pass through this cycle differently. But usually first they realize that they have a problem, then they look for the ways to solve it, and then they choose a counteragent to help them do it. It is important to help a person to pass through every stage and nudge one to the decision of a purchase. You can use test-drives, testimonials, cases etc. for this purpose.