Face planes like the positioning of the eyes etc? Honestly I just wing it but I try to focus on the placement of the ears to figure out the proper angle (the head looking up/down) and from there I can see where to put the nose, mouth, eyes, etc. I still struggle with drawing faces but I try to improve. Also when drawing the eyes I draw them in a curve to align it with the shape of the face so that it doesnt look too flat (I always look at ONE's drawings to see how he does this, I think he's very skilled at it). I think this also applies to mouth angles, a mouth smiling from an angle where the head is upwards wont have the same curves as a face looking down.