Here are some Low-Poly face modeling tips I created specifically for face rigging. Hope you find them helpful.
Rough Organization of Process
1. design phase
2. lattice retrofitting
3. reference edge loop compare to wires of lattice edited
4. removal lips, removal eyes
5. create refined lips and eye lids
6. insertion of lip and eye proper loops
1. make side and front views
2. start from an exisiting face model you created. use lattices to fit face model roughly to images. Each time were done using a lattice (ex for jaw vertices) we can delete history of mesh and create a new lattice for say the forehead faces.
3. draw in where the major problem area edge loops are example Jaw, and neck.
4. select inner mouth face and inner eye faces and remove them
5. use poly spheres to construct new lid. use torus to construct new mouth.
6. scale the eye lid and lips to fit mesh. remove extra faces and connect them to existing face.
Helpful hotkeys modeling for rigging
1. xray toggle
2. toggle view selected
3. edge smooth
4. vertex merge
5. key to go to front view and perspective
6. key to go to side view and perspective
Edge loop references:
Jonathan Paine [isculptmaquettes dot blogspot dot com] (watch his demo reel)
Joy Johnson [njoydigital dot com] (watch her amazing demo reels and look at the wireframes)
Guillaume Dufief [ciadzombie dot com] (look at the wireframes)
Jeremy Ernst [jeremyernst dot com] (read his talk on face rigging)
Michael Urbanek [fuzz-animation dot blogspot dot com] (look at the wireframes pay attention to the 5 corner, and 3 corner areas)
David Suroviec [evadanimation dot com] (watch his demo reel)
Face Modeling for Rigging Book References:
Jason Osipa (Stop Staring: Facial Modeling and Animation Done Right)