Even on regular humanoid faces I have a very hard time with them. Could I get some pointers and/or tutorials? I have Tony Mullen’s book, but it wasn’t clear to me there what I should be doing.
Calvin’s Simple Page has a tutorial on creating cartoon eyes with eyelids (scroll down) and you can take a look at his other models with their simple yet very expressive eyes and faces.
If you want to go the realist route, the Adriana tutorialby mr_bomb is all the way at the bottom of BA’s Community Journal #2.