The paper deals with the problem of designing a teacher's guide which will encourage and assist a teacher to arrive at well-reasoned independent decisions, and respect the teacher's experience and intellectual autonomy. The method described pertains to independently developed materials, not developed for any particular curriculum or teaching approach, thus leaving decisions about their adoption and adaptation to the teacher. A representative sample of teachers was used to obtain feedback information before, during, and after teaching a newly developed laboratory block in genetics for the 11th–12th grade level (17–18 year olds). Questionnaire and interview methods were used. Twelve categories for possible inclusion in the teacher's guide emerged. Decisions on whether to include a category in the teacher's guide were shown to be based on the teachers' manifest degree of familiarity with it, their measure of (or lack of) awareness of its educational potential, and their expressed desires for assistance.