You have already studied the general structure of the face. The next step is to learn to modify the appearance of this structure through the use of highlights and shadows. Although the illusion created may involve making cheeks rounder, chins more pointed, or noses crooked, more often than not, it will include some aging.
In youth, firm muscles and elastic skin fill out the hollows and smooth over the bumps in the bony structure of the skull. But with age and the accompanying sagging of muscles, this bony structure becomes increasingly evident. Therefore, the first thing to do in learning to age the face is to visualize the bones of the skull and to locate them by prodding with the fingers.