[originally posted by Mark, revamped for functionality and completeness by Krazy, And a slight change of name for the definition by URBEXSWATUTAH]
(Term AMEX is short for American Express, as in NEVER LEAVE HOME WITHOUT IT!)
Certain items should always be considered when you are going out exploring. This list will vary greatly depending on what you intend to do and how long you will be at it, but this is a start. Go through these lists and think about the place(s) you are going and what conditions and situations you expect to encounter.
For quickie trips and typical scouting missions: small flashlight or LED keyfob is handy a camera can be nice
For more in depth trips: *small flashlight *backup light source if you will be traveling in dark places *proper clothing for the situations you expect to encounter *proper footwear for the terrain (rubber boots? steel toes? rock climbing *shoes?!) *camera *many people recommend a first aid kit, but many people don't bother either *gloves (for warmth? skin protection? both?) *asbestos respirator(s) and filters if needed *food and water to sustain energy and health *Duct tape(this is too useful not to have) *Blueprints/Maps of the location, if they are available *Crayons, to make small notes for other explorers *Good multi-tool don't leave home without it
For photographically-oriented trips: *camera(s) (duh) *tripod *useful lenses *filters *any other camera accessories you may have or need *spare batteries *extra film/digital media *slaves/external flashes *old-school flashbulbs (great for lighting huge underground spaces) *several varieties of illumination for redundancy and utility (big flashlights for lighting effects, medium ones for navigating, and small ones for working so as to not ruin others' exposures) *comfortable clothing (you might be sitting around a lot waiting for 20 minute exposures and the like) *some snacks *water
For the really insane hardcore trips (bring this stuff only if you really expect to need/use it. A lot of these items can look bad or be difficult to explain without taking a ride in the back of a squad car. think it through carefully): *technical climbing equipment *inflatable rubber raft(s) *collapsable ladder *two way radios *scanners *night vision equipment *first aid kit *emergency rations & supplies *lock-pick set, or some other means of opening locked doors/objects *the list could go on...
In addition to bare essential equipment, there are also essential procedures that should be followed. * make sure someone knows where you are going and when you expect to be back * come to an agreement with the others you are with about what you will do in certain potential situations that could arise, such as detection, injury, arrest, or equipment problems. This way you can all act in the same way and have some kind of advantage in whatever situation arises.
This list could also be expanded quite a bit. Please add to any of these if you see fit.
Additional comment - 11/18/08 - I would also recommend as standard equipment a basic referee's style whistle. Should you injure yourself so as to be immobilized (fall through a floor, break a leg, etc), or get trapped somewhere, a whistle can be heard a LOT farther away than a human voice, and requires no power other than your breath.
Additional comment - 4/28/11 - Maybe this is just too obvious but as long as there's other obvious things like flashlights, cameras, etc.... how about a cell phone? As well as being able to call for help if you get in trouble, most smart phones double as a GPS, which has helped me out of binds when I get lost. (comment by ILPUG- cellphones don't work underground at all, something that would rendr one useless to a tunnel explorer)