You never know when or where your personal history will bubble up. Does this post by Scott at Haberblab sound familiar?:
"At odd times all sorts of personal history comes swimming to the surface. Making me think 'Oh yes, I forgot all about that."'only to have the memory float down again."
That sort of thing happens to me all the time. Something will pop into my head and when I try to remember it later, I can't.
Recognizing the situation, I try to carry with me a 3x5 writing pad and pen so that I can document these things as they occur rather than relying on a balky memory. Of course, I often forget the pad and pen.
Still, it makes sense to find a way to snare those random gifts of family history before they flit away. It also works for shopping lists, appointments and any of those other pesky details that test our memories.
What's your system?