Make the workflow visible
A prototype turns a written requirement into a sequence people can try. It helps reveal missing steps and ambiguous decisions.
Test a task, not a preference
Ask someone to complete a real activity. Watch where they hesitate and what they expect to happen next.
Use the right level of detail
Early wireframes are useful for structure. Detailed interfaces become useful when the team needs to review content, hierarchy and interaction.
Carry decisions into development
Document the important states: empty, loading, error and success. These are part of the product, not details to leave until the end.