If you’re using Preview to sort your digital camera images, here’s another helpful feature — the ability to add keywords to your photos. These keywords will even show up in Spotlight, so if you want to search your hard disk for images using keywords, you can.
Here’s how it works: When you have an image onscreen that you want to rate, just go under Preview’s Tools menu and choose Get info. Click on the Keywords tab, then click the Add button to add a field. Enter your keyword in the highlighted field, click in the white space to finalize your keyword, and you’re done.