The number of options for cataloging and filing digital images is mind boggling. You can search and filter your images by ISO, lens, shutter speed, aperture, camera make, camera model, date, time, location, file type, file extension, whether the flash fired, rating, label, or any number of keywords. Any data in EXIF, any text added to image, or any post-processing modification can be used as a way to sort and catalog images. Most people resort to a structure of dates, places, or some combination of the two.
What all those fancy ways of sorting your images deprives you of, however, is the ability to reassess your work. I argue that the value of your image archive as a whole is so important that you should abandon all but the simplest form of categorization, and even then only use it on a rare occasion to locate images.
To understand this approach, first appreciate that making a photograph is not capturing an objective moment—a photograph captures the photographer's idea. Every image you capture is a snippet of your surreal mind: you tripped the shutter at the time you did because that moment was significant to you. It was significant not only in terms of the subject matter, but more importantly it was significant in terms of all the elements in the scene and how those elements fit within an idea you had in your mind.
The surreal mind communicates through images and impressions: dreams are visual and emotional, and our creative impulses are visual and reactionary. The problem with connecting to our creative, surreal mind is the very fact that it is visual and emotional: we often experience creative thoughts and ideas which are too ephemeral for the conscious (active) mind to hold onto. More than any other artistic activity, digital photography solves this problem of the ages. Specifically, two of the significant advantages of digital images to provide insight into the inner workings of your creativity are the volume of images made, and the ability to view those many images at once.
Each image is a snippet of your creative interest, and each of those images is a tiny puzzle piece in the whole of your surreal, creative mind. Seen at smaller sizes, what stands out about images is not the subject, but the gestalt, the patterns of colors, the patterns of luminence—the elements of the visual world to which you are creatively attracted. It is these patterns of what you shoot that make photographic images literally the memory of your surreal mind laid bare. Each image is like a piece of a dream made visible.
Digital photography is unique in the opportunity it presents to view the ephemeral ideas of our mind. This opportunity is fragile, and immediately lost in our conscious efforts at organization.
Categorization and organization are, by definition, intentional conscious acts. The process of categorization is useful in the formation of associative memories, but especially necessary in making the process of "remembering" or retrieving memories more efficient. We do this naturally: when we experience something, we try to fit it into a conception we already have so that we can concentrate on the differences (which require our attention) and assume the similarities (which we already know without active thinking.
A simple exercise will illustrate this. See how many flowers you can name in one minute, and then do the same for animals. Do this before you read on.
Now reflect on how you accessed this information. Chances are, you did not name random flowers or animals, but rather you thought of (more specifically, visualized) categories that are meaningful to you based on your experience and background. There are countless ways of grouping and sorting the information: flowers can be grouped by color, season, scents, or what you have planted in your garden. But think of what happens if you get stuck in one of these categories—if you are only visualizing land animals, for example, you will cut off access to all the sea creatures you know.
When categorization and grouping are flexible, information is stored and retrieved through multiple associations. When we provide a specific label to a group of images, we strengthen the association of the image within that particular category, regardless of it's relevance or arbitrary designation. This is useful for when we want to find "holiday" images or "vacation" photos, but destructive when we want a peak at what drives our creativity.
If you want to know what's going on in your mind, abandon your efforts of categorizing images. That process relegates them to the conscious world of labels and deprives you of seeing the themes and patterns that can better direct you to developing your photography in a more satisfying way. A better route is to hit that "All Photos" filter, reduce the thumbnail size, and take a look at what your surreal mind has been trying to tell you. I think you'll be pleasantly surprised by the results, and excited by the insights you discover.