/ic/ - Artwork/Critique

This might sound retarded, but during loomis head drawings there are lots of curved/dissecting lines you have to put on spheres right? How do I figure out how much to curve the lines? Is it something you generally learn off of feel? Or is there a method to it?

Pic related, the middle one I tried earnestly on and I know it’s fucked. Quickly sketched the bottom ones and the middle left just as examples for ones that are bad, and another that I tried on