Well if I were doing this I would keep it short and simple, no dissertations for the average DIY. Topic's off the top of my head:
1) Why it's important to use a quality car wash vs dish detergent
2) Choosing a car wash medium: wool, MF, sponge
3) Explain proper use of brushes: wheels and wheel wells OK - not for paint use
4) Benefits of rinseless washes
5) When to clay
6) How to clay
7) Grades of clay
8) What are swirls and how they are most likely induced
9) Dispel myth that new cars with cc don't need waxing
10) Explain what a cleaner wax is and why if that is all they use they will have poor durability
11) Recommend use of OCW or Aquawax if their schedules do not permit time to properly prep and seal
12)Provide tips for cleaning halogens
13) Provide info about this site where they can learn more than they ever thought possible