You have the photographer take the photo with the light source on one side.
You can then increase the effect in Photoshop.
Take that photo of a face where the light source is on one side (photo source)...
...and increase the contrast using
Image > Adjustments > Brightness/Contrast.
Or, a more advanced way with more fine control is to use
Image > Adjustments > Curves to create an
s shaped curve where the darker parts of the face are darkened and the lighter parts lightened - find where on the curve the
s should pivot with the eyedropper you get while the curves window is open.
This won't help unless the photo was taken with the light source on one side.