What you need is to find an internet site that offers serious critiques for submitted images. Unfortunately, I'm not aware of any that really do. Most places I've visited mainly offer comments of "nice pic" or "nice colors" even for the most flawed of images. You might try Photo.net or Photo.sig... but I haven't been there in well over a year so not too sure how good they are nowadays in critiqueing or suggesting ways to improve images.
Best method would be to find a local mentor, or camera club, that's willing to teach and suggest and critique images honestly.