I'm usually looking toward landscapes, or human influence in landscape (I'm partial to barns), then I'll stop and look further at a gallery photo if it has a good sunset or sunrise. Then I'll start looking for the details, is it soft, is it composed well, why is it composed well, is it a good subject, where is that, might I want to visit there, etc. But mostly it's subject (landscape, barns, nature) then the light.