Well....
All of them are underexposed except for the bottles. The bottles picture would be cooler if you would have exposed them from a longways view(or vertical i guess). Watch your backgrounds closely, ( I have this problem, everyone does but simplify it as much as possible, less is more) it can easily destroy a good picture. Another problem is the lack of subject matter, it has you looking all over the picture for something that isn't there. Next time shooting:
1
Simplify your pictures- Walk around your subject until you find an angle that doesn't have distractions
2
Use leading lines so it creates a pathway to whatever you want someone to look at when they see your picture
3
Use the rule of thirds. Cut your frame into 9 squares and try to get your focal points where the lines intersect.
4
Exposure settings
http://tiberius47.deviantart.com/art/Basic-Exposure-Settings-52556187
Link explaining better:
http://www.digital-photography-school.com/rule-of-thirds
There are several websites you can use to learn, check out Ken Rockwells website. It has alot of good info that can get you started.
I figure your using a point n shoot camera? If you do have a DSLR, read up on aperture, shutter speed, and iso settings. It can be hard to grasp, but certain people put it simply or relate it to something. If you have any questions i can help you to the best of my ability. I'm still new, but I enjoy passing whatever i know to others.