Whenever I am commenting in Facebook photography groups about lighting I always go back to this lesson.
I tell people to turn off all the lights in a room, get a flash or use the light on their phone and aim it at a subject. Move the light around and study the effect it has on the subject. So it only made sense for me to make a video of this approach.
For this video I use two styrofoam heads from Michaels that were like $3. Using these heads are great for learning to light portraits since you can really study the shadows. It helps to better understand the Inverse Square Law. Aiming a light from the side gets good moody lighting but can leave a dark patch near the nasal bridge. Bounce / reflecting light can help fill those shadows.
I also discuss getting catch lights in the eyes. Using the light from the phone or even better using a ring light you can emphasize the eyes with cool circles reflecting in them.