I am an organizational consultant who helps design, recruit, and train boards of directors; guides strategic and organizational planning; and facilitates the development of unique and effective client acquisition and retention plans.
Why would you do this [reasons and perks]? Use your reasons to find like minded people to ask.
Approach it as if you were applying for a position in an organization. You will want to find the right industry, the right management team, the right opening on the board [either governance or advisory], the right person to help you. Next create a statement that says why you on this board. Then sell it.