Eyes on their own is always the easiest. I draw them alot better alone then when i actually go to draw a character.
Mouth and nose are pretty easy if you know the exact position the character is going to be placed in..
and all it really needs to be is a line manipulated into either a smile by rasing one end up a little or down a little for a frown or just left straight for a well straight face.
Noses depending on how realistic you want them or traditional anime/manga.. aren't that hard.
Hair is what i usually have trouble with..the hair i draw always looks too flat and chunky.
Ears i hate ears.. they drive me insane which is why my characters usually have long hair so that i can cover the ears up.. but i'm good at drawing elven ears.. for some odd reason...
anyway SQUEE my vid's done it's uploading please check it out.
3nodding http://www.veoh.com/videoDetails.html?v=e150465JeRPcpqQ