OR, THE EASY STUFF
Really, the hard part is done. If you can get the basic form of the head right, you can draw a Manga face. The features are easy.
Of course the specifics of the features change from character to character; and they certainly change with different expressions (in fact you could almost say that drawing a Manga face is drawing an expression). What follows is a basic blueprint for a simple, common sort of face. After you learn this, it ought to be easy to start to use different variations.