Every once in a while I'll create an image that I know I'm going to like before I even process it. Right when I click the shutter I'll make a mental note, "yeah, that one is going to be good..." Those moments are incredibly rare for me, but when they happen I experience a little thrill that can't be repeated or duplicated. It may sound cheesy or cliche, but I think a lot of artists live for that.
The more I try to find that moment the more elusive it becomes. You just have to let it happen. The best one can do is take their camera out with them and remain open to it, but never try to force it. Just point, click, and repeat until it happens on its own.