mickydoo more or less has the right idea. What he's explaining is basically Rembrandt lighting. In a very rudimentary form, it looks something like this:
To break it down as simply as possible, I've just used colors.
Blue: This is your main spotlight/emissive/etc. The blue circle on her face is traditionally called the "short side", and for the best result, the brightest light sources should be on that side. Not always, but most of the time. That blue arrow point to the orange inverted triangle is the light from the spotlight spill over form the short side of the face. This is the key symbol of Rembrandt. As mentioned by mickydoo, again, it should be near a 45 degree angle, aiming downward at the model.
Green: The green circle on her face is often called the "shadow side". Leaving a dim fill light or just shadow here creates a level of mystery and drama. As a said a dim fill light, or even natural ambient lighting should be all that's here.
Pink: This is an optional step, a rim light. It's easy enough to faux this being natural lighting either via a ghost light or a spotlight that isn't in frame. What having that rim will do is allow your model to see light-dark-light, and in that context, creates visual dynamic.
Something like this is done in a similar way to the example I posted above:
Or this, which was done with just a single spotlight on the figure at said 45-degree angle (and two more to illuminate only the background):
