There is lots of great information about using exiftool at http://www.sno.phy.queensu.ca/~phil/exiftool/filename.html. The one I use to manage my photos is
exiftool -d %Y/%Y-%m-%d "-directory<datetimeoriginal" ./
Another pattern that I'm trying out, to play a bit nicer with image browsers. Puts all images from the same month into one directory, and prefixes the file name with YmdHMS_ to make sure chronological order is preserved.