I just started pencil sketching again - I never managed to make anything that didn't look like it was part of a horrible nightmare before. I think it was a question of finding the right tutorials - if you look for art of wei on YouTube, his explanations click for me, and maybe they'll make sense to you too. I haven't drawn a whole face yet, but the one eye I did draw looked very convincing. you'd need to start with shading a cube, cylinder, sphere first - it's what I did first (using other tutorials, but there's a couple from wei too). you really need to understand the sphere before moving on to interesting shapes. also a keyword for getting the face right is the Loomis method.