General consensus, for as far as I've heard, is you should pack with ease of use and weight balancing in mind.
Basically put the heaviest gear high and close to your back and try do distribute evenly horizontally as well to keep your body in balance. Put your FAK and rain clothing easily accessible, just like food which you intend to consume during the day. Water should also always be easily accessible to make sure you drink enough...
My personal pack (highlander 88) configuration:
Main compartment:
-Lowest in the bag: sleeping bag and mat (take quite a lot of space so are light weight/volume wise) as well as evening clothes (as in: stuff I wear to sleep and put on after washing, after the tent has been set up)
-on top of it: my cooking gear and food which will be consumed in the evening or morning (while the tent is drying) as well as reserves for following days
-higher: tent or hammock (weighs quite a lot and will be taken out of the rucksack before the cooking gear anyway)
-above: food for use during the day
-on top of that: my rain coat (+ waterproof overtrousers) and, if needed, a warm sweater for daytime use
-finally: big water bottles
Front pocket: FAK, torch, sun glasses, ... (small stuff which should be easily accessible)
Side pockets: gloves, socks, underwear, and food which will be eaten without really stopping
Top pocket: raincover for the rucksack (might put waterproofs in here too, don't really know if there's enough space)
On the chest and lower straps, I hang a small water bottle and the sunglasses if not used for a couple of seconds as well as my compass.
Quite obvious once you get out to use your gear really... (others might obviously have different patterns depending on their usage, so I wouldn't say this is THE best configuration)