Teaching embouchure formation is such a unique task! Each person's physiology and shape of the lips, thickness of bottom lip vs. top lip is personal , so a 'one size fits all' approach does not apply to embouchure placement. However, there are some general ideas that will help. By thinking of the ideal direction for air as 'across and down', each lip can be assigned a task. The top lip directs the air down: I like to think of anchoring the top lip lightly on the canine teeth, maintaining a slight space bubble between the top lips and teeth. (this is a particularly difficult concept for sax and clarinet doublers who are used to a tight seal here). Try to remind students to not overly purse the upper lip. The bottom lip directs the air across the embouchure plate. Using the moist inner surface of BOTH lips insures more sensitivity. Remind students that the corners of the lips are not upturned or pulled back (like smiling). Make sure that the aperture changes shape depending on the dynamic and register. These simple tips can keep students on track for embouchure success.