A good source of information on using Universal Transverse Mercator (UTM) coordinates is
http://www.maptools.com . That sight also sells very nice UTM grids at reasonable prices.
My advice would be to make sure each hiker has a topo map of the area with UTM coordinate drawn on it, a UTM grid (either on the compass or a separate one), a decent compass with the knowledge to adjust for magnetic declination (17.5 degrees East in Seattle area), and a GPS with fresh batteries and the knowledge to use it along with the map & compass. The idea would be for them to enter waypoints for key locations (starting point, ending point, etc...) BEFORE the hike even starts.
If lost, they could use the GPS to determine where they are, then use the UTM coordinates from the GPS to determine their location on the map, and then give that coordinate to rescuers or use the GPS and the map to track their way back to where they need to be.
When in the field I carry the Garmin Geko 201 because it is tiny, lightweight, stores waypoints, shows my current location, AND allows me to connect it to my computer for pre-loading of waypoints. For that I use some nice software called ExpertGPS (
http://www.expertgps.com for $60 - stores GPS waypoints and also provides on-line Topo maps and aerial photos).
For maps I have been buying from USGS, but recently started ordering weatherproof/tearproof USGS topo maps from
http://www.mytopo.com .
If you can get mapping software to print out maps that preserve the 1:24,000 scale, that is good too, but I've had trouble with that so I buy pre-printed maps.
All of this assumes that the hiker is in a condition (physically or mentally) to walk out of their situation. They need to be equipped to handle the other scenario where they need to stay put and wait for rescue. That is where the gear recommended by Doug Ritter is critical. As general advice for a large group of hikers, my advice would be to tell them to purchase the Doug Ritter
Personal Survival Pak and then suppliment it with the items recommended in the bonus materials:
>Folding knife w/ locking blade and at least a 2.5 in blade that has one-handed opening
>Pocket-sized personal shelter such as a space blanket, bivvy sack, large bags, poncho
>Pocket-sized or key-chain LED flashlight w/ constant-on switch
>First aid kit: such as the AMK Pocket Medic or Ultralight .5
>Personal supply of Water, such as a Nalgene water bottle with Katadyn Micropur MP1 purification tablets
>Personal medications (rotate regularly)
>Waterproof matches and/or lighter, such as the REI Waterproof matches in a waterproof case or a mini Bic lighter
>Personal Locator Beacon, IF it can be afforded
>>In addition, I'd recommend making sure you have a large highly visible "flag". This could be some
bright orange plastic bags , an orange poncho, or similar. Just anything to make you more visible through the trees.
And as always,
>Leave trip plan left with a responsible person and stick to the plan
>Travel with a companion
>Dress or take clothing for the weather
Finally, this gear should be with them on their person at ALL times - even when "just" going into the woods to relieve themselves or looking for firewood. A fanny pack would work well for this. Putting this gear in their backpacks is not enough. There are plenty of stories of people who are separated from their packs for one reason or another (falls, floods, etc...).