It is a common refrain: We don't have enough leaders for the ministries we have - or for the leadership board. Most churches do have the leaders they need but they have not been equipped or envisioned to lead.
The default for most churches is that we try to train leaders "on the job" rather than preparing them ahead of time. This default mode is dangerous in that one is putting untrained leaders in critical spots. It does not work well with boards in particular.
A simple solution is to develop a group of potential leaders that you meet with monthly. During those monthly meetings you can read and discuss leadership books, talk about the ministry philosophy of the church, train in church leadership, challenge them to be growing in their spiritual life and envisioning them for leadership or ministry in the local church.
You will quickly discern who your best potential leaders are and you will be growing them before they get into key roles. It is a simple but very strategic move.