Every new drive is by year. Other than that I don't date my folders in my catalog as I can't even tell you what day it is today, much less what day it was when I shot a particular subject. In my regular catalog I'm pretty unorganized. I import images to their own labeled folders, but I don't break it down further via subject or anything. I do use smart collections for certain subjects though. I also use color labels for different purposes too. For example, red images are for photo merges/composites, green are finished and ready to print or publish, blue are finished images for print that won't go to the web, etc. Ultimately, it works for me, barely, but if I was working as a full time 'tog I'd probably take better care to be more organized.
As has been mentioned, the DAM Book is a good place to start in figuring out how to manage your files. Especially if it's for work, rather than just a hobby.
