Some things that you may want to consider before you critique a photograph:

From www.fredmiranda.com

Effort:

Has the photographer made full use of the facilities at his disposal? Or, are
there things that the photographer could have improved with a little more work?
Does it look like the photographer made an extra effort to capture the best 
possible image under the circumstances, or did he just go with what was in front 
of him? 

Color:

Was the photographer's choice to use or not use color sound? If the photographer 
used black and white, then is the subject of the photo something that is 
normally associated with color, like an apple? If the photographer used color, 
does the color add to or detract from the image? 

Spatial positioning and composition:

Is the subject in the center of the frame? Usually a centered subject looks 
boring, but it works in some cases. Did it work this time? Does anything look 
squeezed up against the side of the frame? Are there big open spaces around the 
edges that could be cropped out? Is there a clear subject that occupies the 
majority of the frame, or is the subject unclear or small and surrounded by 
irrelevant material? 

Direction of attention:

What do you see first in the photo? Is it the right thing? Do you have to hunt 
for the subject or does it stand out? Is your eye drawn to objects in the 
background, rather than the subject, or do you look to the edge of the frame, 
expecting to find something that isn't there? 

Focus:

Is anything in focus? Is it the subject or something else? Is the depth of field 
appropriate? Is the subject contained within the depth of field or are parts of 
the subject fuzzy? Are there distracting elements in the background that are in 
focus which would have been blurred out by a wider aperture? 

Exposure:

Is the photo properly exposed? Are there details both in the highlights and in 
the shadows, or are there large "blown-out" highlight areas or "blocked-up" 
shadow areas? If the exposure is biased towards light (high key) or dark (low 
key), did the photographer make a good choice?