I try to start with a student's current level of a given lesson, and incrementally lead him/her up to the required levels through constant interaction by way of examples, questions, illustrations, multiple choices, videos, presentations, etc. Students normally react very well to this interactive method. I have often started with students around early High School level and led them up all the way to their Professional levels in Math, Physics, Chemistry, Mechanical Engineering subjects, as also in Computer Programming and System Administration / Networking subjects, over several years of learning.
I always encourage explanations from students in their own words. I have taught students in multiple countries - both academic and professional.