Family photo mysteries usually start with one simple — and easily preventable — problem: lack of identification. Think about the unknown faces peering out from your family's old photographs. At some point, someone knew exactly who the people in those pictures were. Unfortunately, you can't go back and ask Great-aunt Gertrude to caption all the images in her album, and you can't make labels that have faded or smudged away reappear (though you might try!).

But you can avert photo confusion for future generations — by labeling the old images you've managed to identify, as well as the present-day pix you plan to pass on. Putting names and dates on your pictures increases the probability that your descendants will keep them. And it's simple to label your photos safely: Just use the right tools and follow a few basic rules.