2 quick hints i find help a lot with this kinda stuff,
1. Human heads are not circles... everyone thinks this because our hair makes it a kind of optical illusion, we have much more of an oval shaped head, also the eyes are in the middle of the head which is why people draw the kinda + on the oval before drawing.... Actually there not exactly in the middle >.> more just above the + , also the tips of the ears are level with the eyes and the nose usually forms below the + and the mouth not much after that...
2. A human body is usually 7 heads tall.. that is to say take your head size and times it by 7 and you have roughly how tall you are... of course no one is "average" so it can bend it to 6 to 8 heads for a human... other fantasy species obviously differ..
I say this because i don't know if you know this or not, and also i know how confusing it gets at times when starting as I'm still not exactly great myself >.> so just passing a few tips that helped me