If working on foot, carry more water that you think you will need, don't know how many people I see carrying one little water bottle, which is great for a short while, but if you get lost or incapacitated, you will wish that you had a hell of a lot more. A combination of hip mounted water bottles and a camel back is a good compromise between a practical amount of weight and water capacity.
Fill up on water and hydrate yourself before heading out, otherwise by the time you are dehydrated, it is already too late to keep your fluid levels up. This is especially the case working or detecting in very humid climates in the top end, in which I find that I constantly sweat big time, and really need to be on the ball to ward off dehydration (working in thick QLD Savannah scrub, reinstating claim pegs). Give salty foods, sweet drinks and coffee a miss. My previous boss would always constantly drink coffee, and end up pissing most of his water out by midday, he always ended up with mild heat stress and headaches by the end of the day.
Probably the 3 things I would never be without working on foot, is decent water capacity, and abilty to start a fire, and carry a decent knife, preferably a survival type one. A small LED torch would also be a good addition.
I've done a few survival courses in my time, and there is nothing like practical experience to make you feel totally isolated, alone and not in control, especialky without the aid of a vehicle with all your goodies packed in it. To be sitting under a makeshift lean-to in +40 degree heat, to shivering next to a small fire in the dirt in near zero temps during the night is an experience I won't forget in a hurry.
