oddly enough Helm, ive always found that tutorial to be too high for beginners, and so very simple for anyone capable of understanding it all, because they've already figured out as much through observation or though ninth-grade physics class.
The overall message though of studying traditional first and studying through observation above all is key. I tend to ask my studnets to stay away from drawing books, because they tend to become formulaic in a way that inhibits observation. Simple shapes into linked shapes is the best way to start, and then once youve got that concept down, theres no harm jumping right into observational study. Most important though is to work from the figure and from fabric if you want to learn. get a mirror or a friend and study every contour, forget all the symbols you have learned, like football eyes or bendy-straw arms and legs and all of those rediculous anime facial expressions that we all love so much.
since you inquired about shading, i would suggest making yourself a nice cup of tea and setting it on a small plate with some crackers, prefereably at least one of them faily dull, and drawing what you see. concentrate not on the forms, but on the light and shadow; youll find that these instead of an untrained intuition define the shapes far better anyway. the tea practice should have most of the problems that you encounter - rounded shapes, flat shapes, thin shapes (if the tea bag string is hanging out of the cup) gradual shadows, cast shadows, specular lights, area lights, reflected light, color regions (if you have colored plate/cups), value regions, texture regions. Its a good speed practice too, because you want the tea to still be warm when you finish the study.
under - good points as well, but i wonder if you could have chosen a better verb than "throw into?"