One neat trick David Alloway used (in fact, he's using it on the cover of his Desert Survival book) involves holding up one's index and middle fingers in a "V" shape, with one's hand held out at arm's length, and positioning that outstretched hand so that the search plane (or whatever you're trying to signal) is between the two fingers. You then reflect the light from your mirror and guide it by watching the spot of light move up your arm and fingers. Upside is that this can be used with any reflective thing, including a rear-view mirror from your disabled car, or a soda can, or whatever.
Downside is that a palm-in "V" sign is construed in England and Australia and other Commonwealth countries as the equivalent of an extended middle finger in the U.S.A. So maybe you run the risk that if your prospective rescuer is a bush pilot from Oz, he'll wind up just flying over you, waving, and leaving you there in the sand.
That said, I really like the sightable mirrors. If you're having trouble with one (as I did at first), you might want to make sure you're doing it outdoors, or, if indoors, in a place where you have ONE MAJOR one-point source of light--something like the sun, or maybe the moon, will work, but a ceiling-full of fluorescent light fixtures won't give you the single aimable spot you're looking for. If that doesn't work for you right away, try holding the mirror at different distances from your eye. Also, using one's arm as a target so that you can easily see where the reflected light is going and then look through the sighting-hole for a dot in the general vicinity of where you see the light on your arm, is a way of getting the idea of how to hold the mirror and what to look for.
By the way, can anyone tell me a place to get the smallest possible sightable signaling mirror? I think I've seen one-inch ones, or maybe two-inch-square ones, but I can't remember where. Obviously they won't work as well as bigger ones, but it could fill a niche in a carry-it-with-you kit.
