It would probably be better to start with some front-view faces, cross sections etc... The nose should be in the middle of the face, then the eyes 4/5ths up the face and the mouth 2/5ths up the face. Since you are drawing Anime type stuff, in this style, I would guess the mouth is much closer to the bottom, the chin is much pointier, the cheeks stick out a bit more, the eyes are masssive...but still start in the top 4/5ths of the face and go down. Another thing to try (when you are drawing from the front) is to draw only the LINE of the mouth, and the under line (or shadow) of the lower lip.