Drawing from the real life is especially useful for someone who is learning to draw. It teaches you that drawing is not simply about holding a pen and drawing the correct lines, but it's also about seeing and thinking correctly. We tend to think in terms of shapes, outlines and symbols, but such things don't represent the reality very well. You should be thinking in terms of form and contour.

Here's a good video about it.

I think this post is a good start:

So forget drawing humans for a while and start painting simple primitives. Cylinders, spheres, spheres with a section sliced off, cylinders which end with a sphere, stuff like that. Don't even color them, just work in grayscale and try to get the lighting right. Use real cylinders or photos of cylinders as reference. Buy some clay, sculpt some simple primitives and draw those. Do it over and over again while looking at what you see instead of drawing what you think you see. The more you do it, the faster you'll get better.

And when you feel comfortable with basic forms, you can start combining them into more elaborate forms. When you use reference, try to see the basic shapes of which your reference form consists of. A human head is like a sphere, with both sides sliced off, attached to a cylinder. Of course, there's a LOT more to human heads. Keep it simple until you're comfortable with drawing tens, if not hundreds of primitive contours together, because that's what heads consist of.

If you're drawing from reference (which you should be doing), try flipping the reference image upside down before drawing a single stroke. This can trick your brain into actually looking at form instead of sticking with the symbolic shapes which are deeply ingrained with how you look at the world. Crop the reference image to a tiny area, then try to replicate it as closely as possible. Then do it again even better. And again and again etc.

So draw a lot, draw from the real life and draw from reference and begin to think in 3D.

I think Drawing on the Right Side of the Brain is probably pretty effective because one of its main point is the above - that you should just draw what you see and not think in terms of symbols when you draw. The underlying idea about the brain hemispheres is pseudoscience, but that doesn't mean it can't still teach useful lessons.

There's an (unfinished) set of posts about rationality and drawing written by Raemon, Drawing LessWrong p2 p3 p4 p5 that might answer your questions (in the articles or comments.)