I can see that you know what you're doing but that you lack experience.
red: These give the eyecorners detail. Should follow sideways all through the ear and around the back of the head.
green: jawline and loop around ear.
purple: walk straight over the head from front to back. they are on a 90 degree angle with the mouth loops. you could use some more density as well for more detailed nose/brows and lips.
blue: this is the way you loop around the mouth area.
orange: need a loop around the mouth seperate from the blue loop to define area between nose and toplip but you seem to have figured this one out already.
all these loops can be divided into as many as you need to make the detail you need.
The cheek area between the red/green/blue is where it doesn't really matter that much and where you try to dump all your loop connections(vertexs with more than 4 edges)
hope it helps. Topo is hard but you're definitely on the right track.