This is a super interesting thread because of how technical it can get, as artmazon said, there's no "right" way fo doing so, everyone has different mental processes, some people need more structure, some don't, like me!
This is a two step process, and both are messy, just a rough idea and general shape/area I want to occupy, but in part two which is lineart
for lineart, although I can make a cleaner version I tend to do a somewhat second sketch from which I start cleaning on the same layer and start doing the lineart
I start erasing things and repainting lines, until it's on a pleasing state, since I already know the general shape fo the character I can give myself the liberty to do it this way, it's definitely messy, but I like it
Some people like to do like 3-5 layers or even 10 I heard once, but the more you grow accustomed anatomy, perspective, etc, the easier it get's, it all comes to preference though.