'Modeling'

Modeling is making images look 3D - this can be done with reflectors so the subject has some light on the darker side of them, or with Gobo (black card) to create shadows and prevent having too much light in one place.

The image needs to be sharp, use a single point AF and keep the eyes, especially,  in focus.
Use Histograms, white balance and spot metering to keep the skin tones looking nice and natural.
The photo is best taken with the subject facing the sun, or, if you want the face in shadow, using a reflector - a piece of white card or shinny card, to reflect the sun back on to the subject and pick out the features; alternately, you can create shadows with a 'Gobo' (black card).
A flash will help to separate the subject from the background by making them lighter than it, it will also fill the shadows in as well.