What to have in your field day pack:
rain gear: backpack cover, rain pants, rain coat
2-3 liter camelback water bladder with external backpack straw (example here), or room for 2-3 1 L water bottles (example here)
snacks and lunch (bring more food than you think you need for the day - especially high protein snacks like trail mix and granola/energy bars)
body wipes for bathroom things, preferably biodegradable (example here)
for women, ziplock bag (for feminine products that won’t decompose)
sunscreen
bug spray
extra pens for writing in your field notebook (you will loose so many in the field)
sun glasses case (the glasses are constantly coming on and off, if it gets dark and stormy it’s nice to have somewhere to put them away)
hiking poles (optional)
vaseline or strong lip balm for chapped lips (example here)
leave room for:
taking off and storing your extra clothing layer
map board if you don’t want to carry it while hiking
rock samples!
Back from the field clean yo’ self routine:
For when you are camping many days in a row…
hiking boots off, sandals to air out feet.
clean and or hang up socks to air out (clip to your tent or a clothes line)
clean and or hang up field clothes to air out (how to wash your clothes in a ziplock)
body wipe bath with biodegradable body wipes (arms pits and private business)
(I keep a ziplock bag in my tent so I can throw wipes in there and then discard them)
5. moisturize hands/face especially if working in desert or high elevation sun
6. before climbing into your tent for the night, clean your feet with body wipes or in a foot bath
tips for keep laces from loosening while you hike, and how to tie your laces if your foot or toes are hurting
Having your period in the field
Two good articles with advice on how to deal with having your period in the woods, this one and this one.
Lots of avid field goers like to use a menstrual cup (because they can be used for up to 8 hours!), here are a couple of videos on how to use & clean them, this one and here.