Power Squdron course is great, but let's face it, for most boaters, 1/2 that stuff goes right of their heads.
geezee has the right idea. Allow me to add a few:
1. Simple in water courtesy...who has right of way and why
2. How to get on and off plane safely (for you, your boat, and your passengers)
3. How to handle your boat in emergency situations and knowing the limits of the boat (hard turns, goosing the throttle, hard stops)....by feel. This is taught at 'how to drive' clinics for teens..and 'test driving' emergency situations under a watchful eye makes one more confident.
4. How to read navigation buoys (e.g. the old red right return trick). Quiz them on every trip and have them 'read' a new one every 4th or 5th trip. Most folks cannot remember all of them at once, go slow.
5. Procedures to start and stop the boat (in order, never deviate). I'm always terrified of forgetting the bilge blower
