[left]kary,
Great to see your work!
I did a bit of a paintover for one of your drawings, hope this helps:
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[left]The main thing to try to do when drawing is to ANALYZE, not COPY. This is something Vilppu stresses and it’s the best way, imo, to go about drawing the figure. There are a variety of great resources in terms of books and DVDs ~ there are Vilppu’s publications, Bridgeman’s books, the Hogarth and Loomis books, etc. All of these guys teach form and structure, and I think if you start to do Master Copies of these artists and of others, you will start to see a great change in your work, as well as in the way that you see things.
I always encourage people to do Master Copies ~ see this useful thread with links to Master Copy Resources:
Master Copy Resources
http://forums.cgsociety.org/showthread.php?t=354836
Looking forward to seeing more of your drawings! 
gnoway,
As you are not a high school student, I have no qualms about encouraging you to do digital work. That being said, I think the best way to master the human form is traditionally (at least at first). I think your studies are going quite well and I would encourage you to keep doing these in pencil. 
purka,
Hi there, welcome aboard!
I took a look at your deviantart account and the main thing that I would recommend is to work if at all possible from life ~ do you have access to life drawing courses? ~ and also to avoid copying the manga style when learning the human figure. I would definitely encourage you as well as others here to try the Exercises posted to the beginning of this thread, and to post your results here. Looking forward to seeing your work! 
neacser,
Welcome aboard as well! What amazing talent for a 15 year old ~ it’s fantastic to see!
These are all very solid studies ~ from what references (life, master works, etc.) are you working? I would very much enjoy seeing more of your work, and would encourage you as well as others to create your own Anatomy Thread, here:
Personal Anatomy & Sketchbook Threads
http://forums.cgsociety.org/forumdisplay.php?f=200
See this thread for information about creating a personal Anatomy Thread first:
FAQ: Can I Create My Own Anatomy Thread?
http://forums.cgsociety.org/showthread.php?t=341167
Links to all Personal Anatomy Threads can be found here:
Anatomy Threads of Individual Users
http://forums.cgsociety.org/showpost.php?p=2817397&postcount=12
Looking forward to seeing more of your work! 
Fl3wk,
Good to see you here, I would also encourage you to try the Exercises at the beginning of this thread, which will get you into doing some Master Copies. 
Great stuff everyone, keep up the good work! 
Cheers,
~Rebeccak
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