Light
signals may be constructed from three different types of light sources.
The first is from a self-contained source, such as a flashlight or
part of the standard equipment of a vehicle, i.e. headlights, spotlights,
landing lights, or warning flashers. The second type is reflected
light, most likely sunlight. Ideally, the best thing to use for this
is a special signaling mirror with a built in sight. In the case that
this special mirror isn't available (which is usually the case), a
pocket mirror, a broken piece of glass, shiny metal, or even ice can
be substituted. To signal with a mirror, shine the reflected spot
on some nearby object or the ground. Place your thumb in the light
so that a corner of the reflectoin and your thumb are lined up.

Then maneuver the mirror, as shown in the picture, to keep the thumb
illuminated as the beam is directed toward a search plane. When the
corner of the reflector, thumb, and aircraft are all lined up, the
pilot can see the flash.
A single campfire can be used as a signal but it is better to have
three formed in a triangle. The first in the triangle should be the
campfire. Next to that should be a large pile (~4 feet wide and 4
feet high) of slightly damp or green vegetation. Build the third fire
the same as the second. Next make two torches to light the fires.
You do this by attaching dry vegetation to a long stick. Set these
tourches by the second and thrid fires. These fires shouldn't be ignited
until rescue aircraft are sighted.