You just need to be open to it. The below is a closeup of the inside of a trash can moments after the copy machine guy dumped the contents of a color ink cartridge. There I was, tripod, DSLR, fast lens, all positioned over the garbage as I carefully worked the composition. It reminded me that you simply never know when or where a picture will appear. For this reason, I feel it's important to your development as a photographer to keep a camera with you at all times. Cell phone camera, point and shoot, DSLR, or anything else that you can create pictures with. By having something by your side, you will be more likely to recognize the opportunites which are all around us. It may not be a grand landscape, or a scenic vista, but don't let that discourage you. There are rarely "perfect opportunities" in photography. It is up to us to make something out of nothing. I encourage you to inspect the details around you right now. Grab your camera, and make some pictures. It may turn out to be trash, or it could be fine art. You'll never know unless you try.