I guess I have the ultimate problem of trying to control 2-1/2 million images and keeping them all straight...so here's the way I do it: xxxx/xx/xx ....year first, month second, day third. For example 20111202 for Dec 2 2011. I put the family name first, a single space, the date, then a subscript (_) and then a sub topic.
For example: Smith 20111202_Bridal Shower. Or Yosemite 20111202_Camping Under Half Dome. The space and the subscript are very important to make sure it sorts correctly. In my case, as a pro photog doing restoration and retouch it's critical. I might have 30 jobs for the same client from different dates or years and I need to find them quickly for revisions, etc.
Hope this helps....Denny Weigand