That's fair...I am new to this afterall but perhaps more specific advice would help. What makes them look like snap shots? I have read a lot about composition and exposure but but putting it into practice is another thing. As you may know it's very difficult to see how to improve your own photos, much easier to tell someone else what they could try.
Sure,
For starters when I look at photography I don't like to see things that I see in my every day life with my own eyes. That tosses out pets and other bland "daily seen things". Now I too love my pets and love to photograph them, but those are my pictures my snapshots (not my images), as I don't really consider them personally interesting if lacking that emotional attachment. YMMV.
Now don't get me wrong daily seen things can be very interesting when put into another perspective.
When I shoot photos I try to think how I can make someone stop and look at this moment that I have captured in my life from MY perspective. It is a very very powerful tool and what originally made me interested in photography.
So for your photos, I like #1 and #5 the best. #1 is made interesting from the rusted metal drum in combination with the sunset. But the exposure is off, this can be corrected after the fact with post editing software, but its best to try to get it correct to save yourself editing time. Were you using a tripod in this shot? If so you can improve your exposure by simply lowering the shutter speed allowing more light to enter since this is a still frame, when trying to capture movement you will have to increase SS and compensate elseware. I also feel this shot could be improved with a bit increased DOF to put that metal tin and the brush around it in sharp focus and the landscape slightly out of focus.
Play with your aperture settings but you must remember your aperture, shutter speed and iso are all directly linked and must balance in order to keep correct exposure. With that being said I never raise my iso from the minimum if I do not need to, I only even consider it if I am not using a tripod and have poor lighting conditions or photographing sports in low light.
A really great way to learn exposure and helped me leaps and bounds was to put my camera on a tripod and shoot massive brackets. f2.4 with a various range of shutter speeds, then stepped it up incrementally in both departments. This gave me my own personal reference to view what apertures / shutter speeds provide what results at certain distances. You can learn DOF and how to influence it this way as well. I use a program called Aperture (for mac) another one is Adobe Lightroom. I know Aperture has a feature and I assume Lightroom does as well that allows you to see all camera settings on a given image very easily. This allows you to simply scroll through your images and see the different effects.
What makes #5 work is the play from the shadows, but whats going on in the background is rather bland and unsightly out of focus construction equipment. If you could have repositioned it to include something more interesting as a focal point with those shadows I think it could have worked.
Hope this helps some.