I would suggest grabbing a few how to draw and basic animation books to help you understand what "works" for portraying certain types of character through simple facial design and expression. I suggest grabbing a copy of How to Draw Comics the Marvel way. They have a great section on faces. Also the book, Action Cartooning, has a very large section on faces and facial types. The Animators Handbook is another great recource and if you're just into the psychological side of how your mind percieves images, try Understanding Comics. You'll never see a wall socket in quite the same way. I could tell you what I've learned from them but it's always best to go to the source.