Okay, since I don't have more than one piece to decide from, here is my short analysis;
The fact that you are drawing from real life means you are on the right track. This is pretty good for fifteen, but my one suggestion for this particular still life is that you shouldn't be afraid of the pencil. Everything is pretty light, as far as the shading goes, so if you can, try to make things darker, have more intense values.
And as far as drawing other things goes, here is my advice. It's an animator's advice, but it is great advice nonetheless.
Draw living animals/people with big, thick, markers. NO ERASING, NO PENCILS. Just get their forms and shadows and shapes, and detail in pen later. Here are some examples of what I mean:
You'll suck with it at first, I PROMISE, but keep doing it. You'll get to the point where you almost prefer pen over pencil all the time... all of my recent ink pieces? No pencil. ^^ For now that is what I can offer, and of course, study, study study real life when you can. Greek and Roman sculpture, again, is perfect for nude life drawing. You can get action poses no one can hold, dynamic antomy, and you don't have to worry about a photo or a statue moving. Try and do these studies in pen, too.
Oh, and also, try to concentrate on shape. Not WHAT you are drawing.
Thank you so much! Drawing shapes as a start was a requirement in this project that I forgot to mention, but it's true! It certainly does make it a hell of a lot easier!
Thanks for the advice, and I'm doing human anatomy studies right now, so I'll post them when I'm done.