3x change of clothes (recommended baggy cargo pants and tee shirt + hoodie) Put your under ware and socks in ziplock bags to keep them dry under all circumstances.
9x meals/snacks
2x foot ware of choice (recommended one pair of combat or high end hiking boots, one pair sneakers)
1x baseball hat
1x boonie/bush hat (both for sun protection in case of unplanned hike or car breaking, same with snacks)
1x multitool
1x larger toolset if you are taking a car or motorcycle or bicycle for roadside repairs.
1x mess set if planning camping or nature excursions
1x some type of sleeping gear (bag, a few blankets etc)
100 feet of paracord...its always handy
1x roll of duct tape...also always handy
2x flashlight and batteries (2 in case one breaks)
1x first aid kit- buy a fairly complete one, don't skimp.
1x canteen
either water purifying tablets or a small bottle of bleach and your research on how much to add to render water safe but not toxic.
Vaccines- hep a/b tetanus, diphtheria, typhoid, whooping cough..actually, just ask your doctor, I don't know what shots you already have and which you don't
optional/etc/trip dependant
laptop
mp3 player
weapon if legally allowed for either a hunting trip or self defence in allowed jurisdictions.
fishing gear and license if nature based trip...great way to spend a few hours
cellphone
radio's either FRS/CB if with companions and going into the bush or a hand-held HAM rig if your a licensed HAM, to kill hours by chewing the fat on the local repeater.
a journal/notepad to document the journy
maps if your navigating yourself
map making supplies (paper, compass, pace beads, GPS) if your heading into the bush so you can map your route both as part of your journal and so you can find your way out.
Life jacket if your planning on a lot of boating.
All carried in a rucksack with attached metal frame and waste and chest cross straps and a garbage bag lining the inside of the main compartment to keep shit dry. (A Canadian 1982 pattern ruck with frame is about 80 bucks and totally worth it)
9+ years in the army has taught me how and what to carry when heading into the unknown.