Learning the capability of your equipment and how it will see a scene you shoot and utilizing that knowledge, I think is a skill akin to that of Leonardo Da Vinci, Pablo Picasso or Rembrandt van Rijn. You think this is a little over stated? Perhaps not. Not only will you notice the shading caused by the light, the setting around your subject and how you want to set-up your shot, but when your new skill is perfected you will be able to estimate with some certainty the shutter speed necessary to render your subject perfectly lit.
As I have personally begun my own education in estimating shutter speed in connection with proper exposure, I understand it takes a little time and thought before pushing the shutter button. I was the impatient student ready to push the shutter button expecting a miraculous photo worth thousands of dollars. Even if I were completely talented, talent can be formed and shaped. So now I understand the value of learning the basics and the power of their effects in a photo. So get ready: Here we launch into a few practical steps to learn and practice in “self-metering” light.
Where is your subject? Sitting in light, with face shadowed? The location of your subject relative to your light source is important to note because a person’s face is a delicate surface to capture.
What is the part of your subject you want properly lit? Eyes more specifically than only the face for best expression. What I meant by a person’s face being a delicate surface to capture is that being so well-shaped it is deeply shaded or over lit. Proper lighting may require a longer exposure time than you are used to, but keep a tripod or mono-pod on hand to help steady your camera.
How is the background lit in contrast to your subject? Is the background part of the photo as you planned? Be sure to plan steps to include the background elements essential to your designed shot.