When I walk around, either outside or inside, I try to keep my eyes open and watch for unusual light and shadows around details. My reasoning for why I like details is due to the fact that I rarely go anywhere new so I get more creative with my vision and even find the end of a handrail to be of interest. Fortunately, the light changes with the time of the day as well as the season so I often see the same object, but in a different light.
I started photographing these kinds of things right after I read the book, The Practice of Contemplative Photography. It was one of the first photography books I read. You can see the definition and look at lots, of pictures by clicking here.