Well, for sure you have plenty of artistic sense, technique comes from exercise and training.

A little mistake in this picture, if the light is coming from her left side, the left side of her nose should be highlighted.

In my opinion the quickest way to learn is training in "Drawing by shapes"

(first attachment)

You can do it by getting an image on paper, mentally subdivide it into objects, observe the shadows and highlights, then draw the general shape of the object, draw the shape of the shadows, then the shape of the highlight
(Second attachment)

I suggest to start with simple objects, like desk effects, but learning is quicker with pictures of birds in mid-air

About people, the procedure may start from neck or from the shape of the face, without worrying too much about mistakes.
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The trick is in not stopping when you commit a mistake, you'll get back to correct it by covering it with another shape.
I mean, if you notice a shadow came out too wide, go ahead and complete the shape, then subtract the excess.

Another concept that you might find useful is "the apparent color" of the object. To put it in the easiest possible way, if you see an object in problematic light conditions, your brain will elaborate and determine the color you would see if the light conditions were optimal. That would be the base color of each object, the shadows of course should be darker, the highlights should be brighter.

Usually for starters every ramp should have a base color, an highlight and 2 shadow colors, the darkest one mostly used to outline details that in real world are determined by the context (Like the jaw or the side of the nose.)