Drawing tutorials are admirable things, but it is well to remember from time to time that nothing that is worth knowing can be taught.
"Everybody has a theory of proportions of the human body but no artist ever see things as they really are."
Theodor Adorno
The human body when measured from foot to navel and then from foot to top of head, showed average numbers very near to the Golden Ratio. 160cm/98cm and Golden Ratio differ by less than 1%. Picture proportions (600 x 371 pixels) approximates the golden rectangle by less than 0.05 %.
Art is good of it contains significant form (see formalism).
First rule : The pubis is at mid-height of the average adult figure.
Second rule (only for fun, not "for art") : the length of the foot is equal to the length of the forearm.
If you look at a portrait and the face is exactly the same to every detail is that art or is it just boring ?