Its really good for a first go, I'm not the best person to comment as i have a head wip on here at the moment. my head modeling is limited to one so far.
The topology you have is almost there. I think you need more edge loops around the eye area. these will give you more detail in those ares. also i think your eyeballs are tiny! they would just fall out of the head. generally you should have an open socket. it looks like you have geometry behind the eyeball. Likewise with the mouth, it may look ok but you need to think about how this would animate -should you ever use this to learn animation- a mouth that cant open wouldn't be much good. Generally people model mouths in radials. by that i mean ovals that get smaller and smaller towards the lips.

check out jays topology thread it should help you out a lot.