Teaching an adult to ride
It's silly, but with the saddle down so that he is able to push himself forward with the feet, ask him to pretend he's running on low gravity, trying to go as far as possible between steps.

On doing this, he can/could/should lean the bike a bit left when he puts left foot on ground, and lean the bike right when right foot is down.

The "secret" is trying to find and maintain the "sweet spot" when the bike is perfectly upright, and at this spot learn to manage the handlebar to keep balance, while the legs would probably be a bit spread and close to the ground.

This should be done on a flat, smooth surface, so the bike could keep going even at low speeds.

Besides that, I think braking should be learned BEFORE pedalling, so the next step would be to stop the bike, then just reduce speed, and THEN pedal with no foot on ground anymore.

I have never tried this, but I think it's how I'd like to be taught if that were the case :o)

Hope this helps.