Begin with function
Describe the job the product must do, its environment, interfaces and failure conditions. A sketch and a clear explanation can be more useful than a polished rendering without requirements.
Resolve manufacturing questions early
Material selection, tolerances, assembly access and process choices affect cost and repeatability. Identify critical features and separate them from cosmetic preferences.
Give each prototype a purpose
Fit, function, appearance and production validation are different tests. Set an acceptance objective for each build, document what changed and preserve the relevant revision.
Prepare for handoff
The output is an agreed package of requirements, geometry, drawings and next actions. Engineering work is scoped to the project; quotation follows review.