I thing the basics are covered by the post above. Everything depends on the amount of stuff you carry, your pack, terrain, climate, etc.
Usually you want the heavy stuff close to your shoulders. Your sleeping bag is the most bulky and you can pack it first and youll unpack it last, so it goes in the bottom.
I have a FjallRaven rucksack with a lot of extra pouches and areas to put things. Knife, compass, fire, part of my money, chain saw, map, sun glasses, mini-torch, etc. go into my pockets, (pants and or jacked). Binoculars and camera are strapped to the waist belt of the rucksack GPS on my left shoulder, the hose of the water sack on my right. Also a small whistle on a short cord on my right shoulder. The water sack is in the (spacious) top hatch of the pack. When walking in the sun (of when its freezing) Ill cover it in a fleece sweater for insulation. Under the hatch my raincoat if Im not wearing it. Left side pocked is the med.kit, right side pocket the rain pants (if Im not wearing them). Extra space in the side pockets is filled with quick rations like chocolate, energy bars, nuts etc.
The back pocked contains maps I dont need at the time, and other flat things.
Inside everything is separately packed into water proof bags. Sleeping bag at the bottom, tent poles and sleeping mat upright, tent in between, cooking gear close to my shoulders, fuel bottle high against shoulders but upright, clothe in two bags (dry and wet) to fill the gaps.
My machete I strapped to the side of the pack, upside down so I can pull it out without taking of my pack. Nothing is on top or strapped to the back. Anything you strap to your pack, tends to dangle, gets lost, gets entangled with branches, makes noise, etc.
I carry my water in a platypus bag. It collapses when getting empty, so there is no moving water to get you out of balance. Also for this I keep fuel bottles (unleaded gas and smoky peated scotch
) upright, less shaky and less chance of leaking.
As said, his can vary. When there is no chance of rain, the rain clothes go deeper. When travelling with public transport, everything goes inside the pack (like camera and GPS), when in the desert, lots of extra water, in the pack and on my body. Most of these things are logical if you think them over.
The most essential items should be on your body all the time. Things you might need quick (rain gear, light, water, snacks, med.kit) should be at hand. The overall balance should be so that you can walk or climb stable and with little effort as possible.