Well.. it takes practice, and I'm still learning to do it - which is why I post daft questions here!
Learning to shoot with a single flash & convertible brolly is really educational, too.
In this case, take #4 for instance.
Look at the catch lights in her eyes - there's a bright dot dead centre, so the flash was on camera.
Then there's a large square patch above the dot, hence bounce flash, reflector or skylight.
Normally with on-camera flash the shadow would be directly behind her, but it's not, so there must be another light source somewhere. The shadow has defined edges so is not a terribly soft light source, hence my confusion. Window light is usually more diffuse than this but it may have been South facing.
It's possible that there will be no catchlights - perhaps due to photoshoppery - or a shadow on a wall so it's always worth looking at the highlights on the skin as well. Then look at where the light falls off, where the shadows are, how dense they are, how well defined the edges are.
In this case there is a shadow directly below the nose with a fairly soft edge - hence light from above - but highly specular highlights on the lips and forehead, hence small direct lightsource. Then the shadow is denser on the subject's left cheek, so there must be another light source somewhere to her right.
IMO being able to take an image's lighting apart is the first step in being able to recreate it, or visualise something and produce what's in your head. I sometimes study fashion magazines & adverts for just this reason. One does need to be aware of how much manipulation goes on in PS though.
edit: This is a kind of basic analysis. There are lighting ninjas who can make an informed guess as to which way round the deflector in a beauty dish was fitted. I worship at their feet