I would say your style is greatly influenced by manga, based off the facial features you've given your characters : )
Your general anatomy is pretty good, but I think it could be pushed even further when it comes to the hands. The arms and legs in the third pic could use a little more attention as well, but in general I think your anatomy is off to a good start, we can see you understand the basic principles of what goes where.
I also think your pictures could become more visually interesting if you refined your line quality more : ) instead of keeping them sketchy and loose, work more a single line quality with thicker lines in some areas and thinner lines in others like this example :
http://thevirtualinstructor.com/images/apples.gif .
Also I think if your worked more on your colours, adding more than just simple base colours, more refined shadows and highlights you could really bring a lot more interesting elements to your images, and give more details for people looking at your drawing to observe, keeping there eyes on your image longer.
I think your pretty much off to a good start : ) I love what you've come up with so far, and I really look forward to seeing how you grow as an artist!