At a minimum, include a brief evaluation at the mid-point in the planning effort and at its end. You also may consider including a brief evaluation at the end of each meeting (about the process used in the meeting). Strongly consider evaluating the project three months and six months after completion.
Use the criteria you established when you wrote the Request For Proposal to evaluate the project and the process used.
Ask the consultant to provide you with an example of a status report that they will be using to track status on the deliverables for this project. Areas you may want to consider include an overall project status report you can share with your board, a report for tracking the multiple deliverables, that shows progress towards the final deliverable and if necessary, a quick tool to evaluate the effectiveness of your meetings with the consultant.
Don’t evaluate based on feelings; specify behaviors that reflect a successful project.