Hoo boy. What ambition! :D

In some ways, drawing is one of the easiest things in the world to learn. You draw. Ergo, you learn to draw. If you keep drawing, you WILL get better, all from putting pencil to paper and trying to make the end result look as good as possible.

That said, there will be issues that you identify in retrospect and go all "Man, that really kept me from moving forward!" Habits, usually. You get used to doing something one way and it becomes second nature, but it may not always be the best way. This usually concerns coloration techniques or anatomy.

Drawing from pictures is a pretty big no. There's a reason why drawing from life is best - your brain learns to translate 3D into 2D. Drawing from things that are already 2D doesn't have that.

Anatomy classes aren't mandatory in the sense of do them or you'll suck forever, though. (Speaking from experience. Uh, hopefully?) What you want to learn is how a body looks. There's pictures of anatomy and muscles on the net and in books. Study them. Don't try to remember everything at once and don't directly copy, but try to remember and visualise how a particular part looks and incorporate your newfound knowledge in your next few drawings. Then, rinse and repeat. Look at people in daily life and analyse how they look from new perspectives - such as the distance between their features, the proportions of the body, how they carry themselves, where the balance lines are. Try not to look too creepy as you do it, too. XD

Drawing things from the skeleton up is always a good starting idea. Hell, you could do worse than sticking to just drawing nothing but skeletons for a while - actual skeletons, complete with at least all the major bones. Then learn where all the fleshy bits go on top.

But in many ways, learning to draw is sort of a spiritual journey. Sometimes you don't get better as much as you learn to push yourself farther. Your standards on how a "finished" work looks in terms of details, realism, lighting and aesthetics keep rising and you're no longer satisfied with how you did it before, which is why works from even a few months earlier will make you cringe and wonder how you could have ever thought that it looked vaguely good. In short, learning to draw is learning to embrace the perfectionist in you. :P

Drawing from life, perusing book after book, studying theories on colour schemes and composition and whatnot, while very, very helpful, aren't really necessary to improve. To keep drawing and simply try to make it as best as you can, every single time, and constantly widening your horizons on what you can and cannot accomplish - that is necessary.


...I'll stop talking so dramatically now. ^^;