As Search and Rescue volunteers, our goal is to help recover a lost
individual. But it's important to understand that we are not just looking for a
person. We should be looking for any physical indication that the lost
individual has left behind. We should be looking for "Sign."
So, what is a sign?
Sign is all evidence, not limited to footfalls, of a person's passage or
presence.
Signs
that are easy to see might include discarded clothing, a lost hat, a water
bottle or candy wrappers.
The harder to see signs are the broken twigs, bruised vegetation and
compressed leaves left behind when a foot strikes the ground.
Can you see the signs in the picture to the right? It's there, but it's hard
to see with an untrained eye.
The field portion of our class is designed to change how you think about what
constitutes a sign, and to train your eye so that you'll see what might
otherwise be invisible to you. That way you can understand the patience and
concentration it takes to notice a sign in the first place. And hopefully,
you'll be a better Search and Rescue Volunteer for the experience, because on a
real search, finding a sign that you might otherwise overlook could mean the
difference between life and death for the subject of the search. Simply put, the
importance of you being "track aware" could someday save a life.

While tracking you might find many of the indications listed in the Tracking
Terms Glossary in one footprint. Or, you might find only the slightest hint of
one of them. Teamwork will be critical for two reasons. 
1) In difficult terrain only one team member may have the right angle to
see a sign, so it is important that everyone contribute to the best of their
ability
2) There are decisions to be made, for example: Is it a track or not? Do
we go on, or do we go back to the last track we were sure of? Should we take
a break?
(Above
right - myrtle and low, hearty ground cover can tough to track in
Left - Tall ground cover like these ferns are much easier to find sign in)
By focusing everyone from three different angles on the "Prime Sign
Area" determined with a tracking stick, the team will eventually find some
indication of a footfall. Then you work it as a team to find as many items as
you need as a team to convince yourselves that you have a track. If you don't
find anything else after a focused team examination you must decide as a team to
go back to the last track and start the process again.
After gaining a little experience, some prints will almost magically appear.
And I don't say "appear" lightly. There are times when you can look
and look and see nothing, and then one little item is spotted and suddenly, the
entire footprint appears to the whole team. I believe this phenomena is a
direct result of training your eyes to see sign. 
(Right - A marked line of sign in difficult tracking terrain)
It is helpful now and then to stand up and look back at the marked "line
of sign." That is the line created by flagging each heel print that
indicates the path the subject has traveled. The line of sign tends to go in a
relatively straight line because that's how people walk, unless a natural
barrier is in the way, like a fallen branch or a large puddle. Then you have to
figure out which route they took around the obstacle.
The goal of the tracking team is to move along, marking the line of sign as
fast as possible while remaining sure that you are on the right track.
Don't always look down. Rest your eyes now and then and use common sense.
When you arrive at tall ground cover you'll be able to track quickly.
(Right - a footprint in the sand)
Finding
an obvious footprint in the sand or mud after tracking through difficult
terrain will be a welcome sign that you are on the right track.
Of course, the ultimate goal is to recover the lost individual.
Your knowledge of tracking and an awareness of what constitutes sign can make
you a more effective search and rescue volunteer in the field.
Our thanks to the Central Adirondack Search and Rescue Team
http://www.theforagerpress.com/adk/mantrack.htm