Even tho Photography is dealing with light and my Art training was in Pigment --I have found, not only here, but in other areas of life, the basic instruction I received in art class in my youth, high school and collage were essential in learning to have that "artist's eye". While natural curiosity is nice, I think it can also be learned.
A book I really recommend is for non-majors. The exercises the author uses are many of the same I was subjected to in college -- and the same ones used for pre-school "training" classes.
For anyone looking for instruction on what to look for in composition or in PP skills, I highly recommend Drawing on the Left Side of the Brain: http://www.drawright.com/
There are probably blogs, tutorials and youtube videos out there as well one wants to save money and is willing to google. The exercises are pretty basic stuff. The author of the book just has them all gathered in one spot and does a great job of instruction.