Many charter boards struggle with implementing their original vision. Even if the founders completely understand the vision themselves, it's difficult to find a lead administrator who agrees with the philosophy and is able to implement it accordingly.
One way for the board to define its vision is by creating and using a strategic plan. The process involves first discussing the vision and mission of the school to make sure everyone fully understands it and agrees with it. Then the board delineates the school's strengths, weaknesses, opportunities and threats. These are both external and internal. The board defines the various functional areas of the school system and creates annual objectives in line with their long-term goals. Here's an example of the Woodrow Wilson Academy Strategic Plan--an excellent model.
There's also a training module available for strategic planning at: http://www.cde.state.co.us/cdechart/guidebook/gov/index.htm
Every charter school should have a strategic plan because it's how the governing board speaks with one voice rather than individual priorities. The plan clearly communicates to administration and staff what should be accomplished within each school year, without being overly burdensome. The principal evaluation should be tied to objectives in the strategic plan. The plan is also an effective means of communicating to parents and stakeholders what the board is working on and what they intend to accomplish.