Here's one I see a lot
Eyes are set somewhat into the face and surrounded by a rim of bones, and as such they never really touch the side of the face. I know you say, but krikri, cartoons! And I'm cool with cartoons, but I actually find this useful even when cartooning. Remember hyoomans are predators and our eyes are in the front of our face, only slightly angled away from each other.
And if eyes are spheres, it follows that eyelids sort of are too, and have a thickness. I know it wont have a hard edge there, but you know, those hard edges are so fucking useful when drafting. Just blend the shading later.

First face is based on a critique for aishamint, second is loosely based on something by arthurh3535 on HF.

The human face has some great geometry to play with when drawing.