1) Make a save profile for creating faces.
2) Import faces into a face library plugin which can be loaded into TESCS for fine-grained tweaking.
3) Import the face into a save with the necessary plugins loaded and look at the face in a variety of lighting situations: starting cell, outside in the sun, in interiors, clouds weather, at night, etc. Do not depend on TESCS lighting or lighting in one location.
4) I would go with Improved Facial Textures over Natural Faces, and install Caps Admin's Smooth EGT for whatever head your character will/may use.
Edit: What body replacer and races are you considering? There are different textures available to match the different bodies.