Less is more (as i'm certain you've heard before) and it's especially true for longer trips.
That backpack will get heavier the longer you travel, so choose each item carefully.
One Man's List
My apologies for being so short sighted but this is really a male travelers list. There are items here for women too but this is far from what a girl would travel with. Also, a complete list for women is damn near impossible as girls are so particular about certain things, and their styles are so diverse from one to another. I have yet to really research the topic of female travel essentials but for now girls, review my lists and take what you need from it.
The girl in the story below could have used the "Less is more" tip too.
Backpack Checklist
Travel Essentials:
Passport(s)
Bank/Credit Cards
Student Card
Foreign currency
Clothing:
Backpack with day bag
1 hat
3-4 shirts (cotton is fine)
1 "quick-dry" shirt (for travel days while wearing backpack)
Lightweight boots with ankle support
6-7 pairs of underwear
2-3 pairs of wool or "quick-dry" socks (no-cotton)
Sandals/flipflops (for showers, bathroom)
1 pair of "quick-dry" pants
1 pair of jeans (optional)
1 bathing suit
1 pair of regular shorts
1 belt
1 lightweight sweater/jacket (No Cotton!)
Rain protection cover
Technology:
Compass
Multi-tool (pack with checked luggage, not carry on)
Digital camera w/large memory card
1 extra camera battery
Camera battery charger
Camera cord for CPU
Pocket-sized tripod
Phone
Small Essentials:
Sewing kit
Toiletries bag for toothbrush, toothpaste, floss etc.
Watch/clock
Headlamp / Mini flashlight
Sunglasses
Passport holder
Small Laundry sack
Travelers cheques (good to have some backup)
1 travel towel (never cotton!)
Earplugs
Travel Guide
Plug adaptor
Pens (Red, Green, Blue)
Notepad
Plastic cutlery set
* the term "quick-dry" refers to synthetic fibres such as Nylon and Polyester. Also refers to natural fibres like wool, bamboo and hemp. These fabrics are used to produce durable clothing that dries quickly and resists bacteria which cause odours.
7.3 - Toiletries Checklists
Cleaning yourself so fresh and so clean is one of the simplest ways to feel personally rejuvenated while traveling. Shaving your stubble, cleaning your ears and clipping your toenails may never be taken for granted again after a couple weeks of backpacking.