Final answer:
The principal should place the most emphasis on whether the activity matches defined school goals and priorities when selecting professional development activities.
Step-by-step explanation:
The principal can best promote effective decision making by guiding the staff members to place the most emphasis on Does the activity match defined school goals and priorities? when evaluating each professional development option under consideration. This criterion ensures that the selected activities align with the overall objectives and priorities of the school, leading to more focused and impactful professional growth for the teachers. By prioritizing activities that directly contribute to school goals, the principal can ensure that the professional development efforts are relevant and beneficial for the entire staff.