Some of mine are learned in the military where camping was "the field" and it was all about carrying the minimum.
Depending on where your going:
Fire starters
Bear proof food storage
(rope over a tree works well, just don't put it near your sleeping area
)
Baby wipes
Green soap for washing if you're near fresh water
Gold bond powder
(foot variety will hurt your junk, so get body powder
)
Duct Tape
Ground cloth/tarp/poncho
Layers
Thin gloves
(fingers are really sore after a few days of roughing it
)
Advil
deep in your bag, hide some goody that you can remember on day 3 for me it's pink snowballs. Nothing says the opposite of roughing it like PSBs...
Plenty of ammo, weapons cleaning gear, batteries for the radio, satchel of C4, and your gillie suit...
Oh seriously though, a knife of some kind, small works best for doing stuff, but where else can you wear a big ol KaBar without getting arrested?
I have done over 2 weeks with a small backpack with a few essentials and food dropped for us
(don't recommend it
) and I've done a 3 day Colorado River fishing trip with my pops with a boat full of stuff where we ate awesome steaks, trout, asparagus, etc. either way, camping is fun.
Be safe, Have fun...