A backpack of the highest quality with the best fit is still only as good as the packing job. Loaded the wrong way, the weight will hang heavily on your shoulders, put painful pressure on all the wrong places, or pull you off balance. Here's how to load a hiking backpack for maximum comfort and enjoyment on the trail.
First of all, separate your gear into three weight-designated piles: light -- items such as your sleeping bag, sleeping pad, and clothing; medium -- stove, water filter, and fuel; and heavy -- your tent, food, and water. This way you get an idea what you have to pack, and you won't forget anything as you load each area of the pack.
Generally, the heaviest items should ride closest to your back, and between your shoulder blades. If you will be hiking on cut trails, place the heavy items higher. This will help transfer the weight to your hips, which are best suited for supporting heavy loads. If you will be bush-whacking, hiking cross-country or climbing over rocks, pack the heavier items lower. This placement will keep your center of gravity lower for better stability.
Your sleeping bag should go in the bottom, along with other light items that you won't be needing during the day. If you carry a bear canister, as more and more parks are requiring, place it against your back in the main pack compartment or lash it under the pack lid. Work your other items in, packing tightly and filling every space. It helps to keep related small items, such as first aid, repair kit, or hygiene items, in stuff-sacks, color-coded for easy identification.
Pack liquid fuel lower than your food in case it leaks. Better yet, carry it in an outside pocket; many packs have mesh side pockets that are perfect for this. Try not to lash things onto the outside of your pack, but if you have to, secure them from swinging so you don't lose your balance. There will be some things you'll want to access frequently during the day. Things like your map and compass, sunscreen, snacks, and rain gear should be packed in the outside pockets or in the top lid. When you have everything loaded in your backpack, tighten the side compression straps to snug it all down. You don't want the load to shift just as you're boulder hopping across a river.
It will take some trial and error to learn the best way to pack your particular gear for your pack and your body. Once you figure out where everything rides best, don't mess with the system. Always pack things in the same place every time. You'll always know where to find what you want, and there's less chance of losing something.
A quality backpack that fits properly will enable you to carry more weight. A rule of thumb is that you don't carry more than 25-30% of your body weight, otherwise you risk injury. If your pack is too heavy, look into lighter versions of the gear you now carry. Using lighter gear overall allows you to use a lighter backpack, helping you to shed pounds from the entire package, and leading to a safer, happier hiking trip.