Learning and Instruction

To be honest, I don't think that you need to worry too much; it'll come to you naturally if you ask me!  Now that you've been made aware of lighting, you're going to pay more attention to it/seek it out, and that's the most important part of art, is just "learning how to see"!

Of course, that being said, there are still lots of things you can do to study it... though, as you already said, studying from life is most of it, sorry.  I think that, while doing your figure drawing, you should also try to learn lighting at the same time, since lighting depends on a serious understanding of the volume of a form!  My advice though would be to avoid straight-on lighting (eg. senshistock), since it has a flattening, paparazzi-kind of look; try to go for more dynamic lighting (aka ones that use only one light source set not directly in front of the model.  I just skimmed through this figure drawing tool and it seems to have some pretty nice poses with dramatic lighting: artists.pixelovely.com/practic…
For this, it can be simpler to apply just one tone of shadow.  A toner marker or just big flat graphite piece works well: Scan422

Idk about breakthroughs or whatnot; but this semester I was auditing a lighting class which was geared more towards photography and film, but it still helped me out nonetheless!  It was really fun to learn about portrait lighting, since it helped me see how dynamic it can be to change up how a face is lit.  This tutorial isn't the best, but it shows you the basics: fc07.deviantart.net/fs41/f/200… and it's interesting to see how light affects the shape of the face!  Don't just look at it, though: sketch out each of these to see how the lighting affects the form, and I think you'll begin to get an idea of how to do lighting.  

And of course, this tutorial is just great for art in general but really covers a lot of lighting if you haven't chanced upon it yet: androidarts.com/art_tut.htm

Basically, you could try to start doing this just by sketching a light source into every picture that you draw!  You don't need to render out a lamp or actual physical object, of course; just draw a little circle/light bulb icon, and then just refer back to it constantly as you try to figure out where to lay the shadows, it's as simple as that hahahaha.  Good luck!!