As mentioned above, I would recommend reading through the tutorials in those links, they can really help someone who's just starting out. Although, looking at your Exif data, it seems you used the manual setting on your camera instead of just setting it on automatic like so many new photographers do, so I applaud your efforts. :thumbup:
1. This shot is underexposed due to having poor ambient lighting and not using a flash. Consequently, you had to use a slow shutter speed (1/40 sec), which is why the picture isn't perfectly sharp. Even those with a very steady hand have trouble eliminating motion blur completely at that speed and lower. The white balance is off, but that can easily be corrected in post-processing software. You can tell it needs to be adjusted because the snowmen are yellow, rather than white. Composition-wise, I can see what you're trying to do, which is focusing on the snowmen. But a successful shot needs to be more complex than that - why do you want us to look at the snowmen? What is it that's special about them? The two smaller, out-of-focus snowmen are a bit distracting, as is the red shiny thing in front. Lastly, try to get get the whole subject in frame rather than "cutting off the feet" (a problem that occurs when many new photographers shoot people).
2. I'm not sure what this photograph is trying to convey to the viewer. The Nike embroidered tag that seems to be the subject of the photo is not completely in focus, which detracts from the quality of the shot. This is caused by the large aperture you used (f/5.6), and again there is a slight motion blur caused by the low shutter speed, which in this case was 1/30 sec. A good rule of thumb to start with for handheld shots is that you want to try to match the shutter speed with the size of the lens or go faster. For example, if you're shooting with a 100mm lens, you would want to shoot no slower than 1/100 sec to minimize motion blur. For this shot, since you were shooting with a 55mm focal length, you would want to be no slower than 1/60 sec, which is the closest the camera offers to 55. There is also a very large hotspot in the top of the image caused by what looks to be a very close ambient light source, which is quite distracting.
3. The issues on this photograph are basically the same as the other two - poor lighting, slow shutter speed, large aperture, etc. The lack of shadows in this shot also makes it a bit boring, IMO.
You know what all this means right? You get to go out and take some more photographs!

The critique is not meant to be harsh or personal (a lot of newbies make that mistake on this site), we're just pointing out technical flaws in the photographs so you can go and correct them when you take some more shots.