Where to really learn the "theory" behind Loop flow, and sculpting Pardon the title, I am aware that topology is generally a lesser concern with sculpting, but I've been wonder if there was a book or lecture - perhaps on youtube or elsewhere - that could explain both why an artist would aim for a particular loop flow and what general method he or she would apply to sculpting?
This site isn't particularly well suited for these broad answers, but here you go anyway :D 

topologyguides.com is a great resource for learning about proper topology. For sculpting resources, check out YanSculpts and Zacharias Rienheart on youtube.