What I do is put the lighter colours in the middle of the part (by part I mean leg, body, arm, etc.) and as it goes outwards, the colour becomes darker. Some professionals do the lighting from an angle, from the side or diagonally infront, for instance. I start by putting the colours in the correct places (no detail yet), start to put the small details like face, maybe hands, clothes detail. Then do the shading. Don't do really simple shading so that the colours are like rings, like on the body and legs, the shading pattern isn't simple, instead it's a pattern being shaded. The hair can be done too, but I forgot (Sorry!). Professionals do some different coloured shading, to make it more interesting and colourful, and isn't the same colour but darker/lighter. I do not know how professionals do it, (Sorry! Idk how they do it) but that's some shading and skinning advice from me!

P.S. I'm not a professional, I just started, so if you want some expert advice, ask a skin shading pro!