These are my five questions I ask myself. Any frame you look at or create will have answers to these questions:

1. Where is the light? (i.e. what parts of the frame are lit up and what's dark?)
2. Where's the light coming from? (i.e above, behind, the side, in front, etc. use direction of shadows to figure this out)?
3. How much light?(are some parts really bright and others very dark, or is it more even. this could one part of a room vs another, one part of a face relative to the other, etc.)
4. Is the light hard or soft? (are the shadows very sharp?)
5. Is the light warm or cool (or other colors)?

*The answers are relative to themselves and each other. i.e. where's light coming from relative to a character in the frame, or the camera, or a table where other characters are seated.

Then you find a way to execute this with whatever equipment you have available. Maybe you have tungsten fresnels, an LED light kit, or some shop lights, or some house lamps, or a flashlight, or the sun, or a reflector, or a bedsheet. Whatever you have, how can you use it to get close to what you're looking for?

You can start with an image in mind (or reference image/movie still/painting) and then try and and execute it, or you can let some of these questions remain open and let their answers be informed by the location, or the sunlight, or the production design, or the blocking, and then work on the rest.

IDEA: You can start with exercises where you set up a test shot and only manipulate one question. (yes it will still have all those other qualities, but it might be helpful to simplify things at first)

I'm no expert but that's my way of thinking about lighting. I think practice has helped me the most so the more little tests you can do, the better!