The most fun, for me, in any shoot is playing with the light. Be it natural, although I always have at least one light of my own, or a studio setting with an almost unlimited combination of lighting. The process of imagining the light I want on the model or set, and then lighting it up to get exactly that look, is very satisfying to me.
Even the simplest of shots typically involves a perfect combination of light and camera exposure. I've learned to imagine the image as I'd like to see it. It becomes almost a game. Making the lighting match what I imagine isn't always dead on first try of course. Re-adjusting the light, moving it just a little, using a grid, or not, and then seeing exactly how it looks when you shoot it. In studio it can be shocking because the ambient light is over powered by the strobes so everything could be very dark with a narrow beam on the model in the shot, but in studio everything looks fairly flat. Modeling lights help a little but frankly, I have learned over the last 5 years to 'feel' how the light should be.
Of course, I have a light meter and sometimes use that to get my camera close to the right exposure, or to adjust the lighting up or down to be what I'm looking for based on what I want to use for an aperture. I tend to shoot lower than observed typical. Often down in the f1.8 and f2.8 range since I'm usually leaning towards artistic. If it's fashion I might crank it up to f11 of course, and this is where the meter comes in handy.
When I started out I spent a LOT of time looking at ads in Elle, Playboy, and just about any magazine and often more at the ads than the content. (The ads in Playboy...really!) I would look very close at the eyes and shadows and see just how it was lit up. Looking at the eyes shows the highlights and often you'll actually see the octobox or ring light or even a pair of lights. It's pretty rare that I've seen the highlights in the eyes modified to hide the lighting scheme since it's not a secret. So, first the eyes, then look at the hair for highlights from overhead lights or even lights from behind. Rim light on the arms and face are the other clue.
The most interesting photographers that I follow are magical with their lighting. In their shots they are crisp, clean, and you can't really tell where the light is coming from. I think they use a large number of lights and have learned to be so subtle with them that they wash the subject without taking away the highlights. This, indeed, is an amazing talent and something I'd love to achieve someday.
Check out Gregory Moore's model shots (his landscapes are amazing too!)
We've always known exactly how light worked starting with the first time we opened our eyes. Now we have to control light to do our bidding. Not a hard task, just takes a lot of practice.