In my mind's eye, I visualize how a particular... sight and feeling will appear on a print. If it excites me, there is a good chance it will make a good photograph. It is an intuitive sense, an ability that comes from a lot of practice.
Other quotes by Ansel Adams
When I'm ready to make a photograph, I think I quite obviously see in my minds eye something that is not literally there in the true meaning of the word. I'm interested in something which is built up from within, rather than just extracted from without.