Who Should Be Involved?
Prototyping requires effective communication between management, users and IT.
The classic idea of having management and user project champions still holds strongly. Without project champions IT groups will always struggle with identifying and adding real value to any project.
Asking the project champions to identify and then design the top five (say) most important real value additions, then fully implementing them, will sometimes get their complete commitment to a project and reinforce the benefits of thinking clearly, as a group, about real value, as opposed to getting lost in a maze of trivial value items like radio buttons, drop downs and trees.
At this stage you should review the topic What Adds Value?