Make a fully functioning model of your new product to test and perfect it.
Prototyping is building an initial physical, functioning model of your innovation. As such, it helps you verify the design of the supersystem—say, a bicycle—as well as the interoperability of the subsystems—the drive train, gears, brakes, tires, and so on. A prototype also tests the robustness of your design and its sensitivity to uncontrollable factors. Additionally, prototyping helps you verify that the required resources and processes are available to support full-scale production or delivery of your innovation.
Prototyping is typically leveraged by product or component manufacturers who need to prove a new design concept, or when the design is particularly complex or expensive to produce. By working out any issues before the design goes into full production, prototyping helps prevent rework and the costs associated with tweaking functions when the product doesn't work in the real world the way it was designed on paper.
If you've never done prototyping before, you can benefit by working with someone who has. For the most part, though, expertise on the product's specific design requirements is the main prerequisite.