These judgements can cover such issues as the breadth of your coverage, the depth with which you cover particular topics, and the sequence with which you address topics. The most likely source of expertise is likely to be in your own department. Another option is to ask for judgements from colleagues at other institutions. Most of us regularly consult with people at other universities about our research. Perhaps you are already doing this.
Many disciplines have organizations devoted entirely to the teaching of that discipline.
These organizations provide listservs, conferences, and journals to support discussions of teaching issues in the discipline. One quick way to get pedagogical information about content is to search the increasing number of course syllabi posted on the World Wide Web. Once you have found these syllabi, you have also found colleagues with whom to consult. All of this is a lot of work, and contributes more information to what is already a flood. I suppose the answer to that depends a lot on your model of professional competence.