Drawing on the Right Side of the Brain takes a lot of its guidance from a book called The Natural Way to Draw by Kimon Nicolaïdes. The latter is more of a textbook with practice schedules and the like, but is a very good guide to go from nothing to decent in 6 months.
The best drawing guide for ULTIMATE beginners is one that (1) lets them believe they can draw (2) lets them actually draw stuff (3) lets them draw NICE stuff such that they think "wow I can draw!" and become motivated to draw more.
https://i.imgur.com/Ch2zqF7.png
https://i.imgur.com/qOHOwK0.jpg
https://i.imgur.com/spGlWE5.jpg
I made these three drawings upside down.
This technique comes from "Drawing with the right side of the brain" and although the science is a bit dated you have one part of your brain (say the left side) that really enjoys naming things, recognizing things, putting things in boxes. This part of the brain causes people to draw eyes like an elipse with a circle in it while this is almost NEVER truly the case. On the other hand, there is the right side of the brain that does mathematics, is rational, etc. etc. This part of the brain is only concerned with shapes, lines, form, direction, etc.
When you turn the reference upside down your left side of the brain shuts down (i.e. it doesn't make any sense anymore) and the only thing you see is lines, forms, directions, proportions. Drawing this way people, who think they can't draw, create really really beautiful drawings!