In November 2016 I started to study the construction of the head and the first resource I used was Alponso Dunn's chaтnel and his videos for beginners:
2. Profile and
There are also several videos about facial features.
Alphonso is a great teacher, he always explains everything thoroughly. There are many more tutorials on his channel. I completed every one of them. I loved the idea of watercolors with the solid liner outline, and all these beautiful flowers and birds. In watercolor Alphonso uses the glazing technique, it's much easier for beginners than wet-on-wet and it doesn't require any expensive paper. I did all the exercises on the very cheap one.
So I highly recommend Alphonso Dunn's channel for beginners,