Hazel from Noodlesoft is a “personal housekeeper” for your Mac. It can organize files into folders, archive files, open/import files in specific apps, clean up files from apps you trash, and much more, all based on rules you create. Have you ever set up an email rule to file messages? Hazel is that, but for all files on your Mac, and much more powerful.
Before you run a Hazel rule, though, you would be wise to run a dry run by clicking the preview button (image 1). Even better, when in preview mode, you can check why the rule caught or missed files by clicking the info button (Image 2) next to the file or folder. This is very handy to verify complex Hazel rules with Subfolder Depth or Sub-file/folder Count as conditions.[thanks Gerard!]