Whether a group of founders starting a new charter school or an existing board looking to replace or add members, all charter school boards should constantly be looking for prospective board members. Some boards have a formal committee for this, others do it informally, especially in small schools.
Ideally, board members shouldn't be added to the board unless they've come up through the ranks; serving on board subcommittees, for example. Through committee work people demonstrate if they're more interested in the title/position or if they're simply about "getting it done" without caring who gets the recognition.
The number one thing to look for in a prospective board member is their character. People with agendas, egos or looking for praise, shouldn't seek a position on a charter school board. The work is hard and there should be little public acknowledgement for the successes. After all, it's the kids who should shine in a charter school, not the adults.
Many board members have asked me over the years about what types of expertise they need on a board. Yes, it's good to have people with legal, facility, financial, or educational experience, but it's not critical. It's more important to have a group of people with wisdom, courage, humility, honesty, and leadership skills. Learning how to govern a public school is something that can be learned. Rarely do people develop the integrity needed to lead a school, if it isn't already inherent in their character.