The application of keywords is such a useful tool for. I apply these when I import from my card. It takes a bit of time but is so useful if I want to find that image a year or two from now. It depends on how descriptive one is and I take mine to a much detail as possible. Say I shot a wood duck, my keywords would be bird, migratory bird, duck, wood duck and any other things that could be visible in the image. If I want to search for this image in that year or two later I use any or all of these and it will limit the view to just these. This can be in Bridge, Lightroom or whatever you happen to use as a cataloging system. When you are saving for display on systems such as Flickr these will carry forward when you save the file as long as you are not using the save for web feature which will nuke all of this from the new file.