drawing - How to study anatomy as an artist?

I am painfully aware that nearly all my paintings and drawings seriously lack in terms of proper anatomy. The figures ofen look unnatural, twisted, deformed etc. More advanced colleagues told me I need to work on my anatomy.

But here's the problem: how do I do that?

What can I be doing to help my practical understanding of anatomy and the ability to apply it? Cause I studied some anatomy textbooks and I have an idea of the bones and muscles of the human body, and I can tell the difference between the lats and traps. Still, I cant apply it to have realistic looking figures and heads.

What should I be doing? Drawing skulls and then faces on them? Painting over skulls on faces? Same for figures - should I be drawing bones on photos / well drawn figures? Should I be drawing the pics from anatomy books? Are there any others I should be doing, that I cant even think of right now?

I want to have a practical understanding of anatomy, I even bought some books (like Tom Flints & Peter Stayners anatomy for the artist), but I dont really know how to use them! There are just some cool drawings of people in different poses, but no actual advice on how to practice it and learn it!

edit:

Also, besides advice on what I should be drawing, I would welcome advice on how I should be drawing. I mean the things i should have in mind while studying. Should I be trying to envision the form? Should I try to imagine the muscles beneath the skin while i draw nude figutres? Or maybe I should be trying to simplify the forms? These are just examples of the type of advice I would like to recieve.

Please note, I want to study anatomy in order to be able to draw anatomically correct figures from my imagination later, when Im more advanced. This will probably affect the way I should be studying anatomy. Making an analogy to studying rendering forms and lighting, I was once told: "mindlessly drawing just what you see wont help you improve your rendering skills for imaginative objects. Try to think about why a shadow is placed where it is and why is it shaped so, why os it soft or hard, where the reflected light comes from etc".