Of obvious importance is tying the evaluation process to the school improvement process (which includes professional development.)
What schools are doing this particularly well? What schools have their resources available online? I have some good paper resources from the Randolph School, and Holton Arms School. I really like the "bands of service" model which divides the evaluation process into three categories: new, intermediate, and veteran teachers. The evaluation and growth process includes mentoring, seminars, peer coaching, admin, peer, and dept.chair classroom observations, student & parent surveys, and action plans for performance improvement.
What does your school do? What do you think makes sense? Do you have resources online that you can link to here?
NAIS Principles of Good Teaching are one good resource.