Your backpack should be packed to make it easy to use throughout the day. The method of packing is more an art than a science, and depends on your preferences and experience. These are only suggestions.
The Main Compartment
In the bottom of the pack go your sleeping materials: sleeping bag, sleeping pad, and pillow. These items are used at the end of the day, so they can be at the bottom of the pack where things are not so easily accessed. They also provide some padding for your lower back, making your pack more comfortable to wear.
Above these, pack your sleeping clothing and any other clothing. It helps to have a large, lightweight stuff sack for the clothing to go into. This will prevent it from exploding everywhere inside your pack. It also enables you to use your clothing bag as a pillow and avoid bringing a separate pillow.
Additional items, if any, could fit on top of the clothing. For instance, a compact hammock, book to read, or anything else special you may be bringing.
At the top of the main compartment goes the food. Pack full meals at the bottom and snacks on top.
Finally, if you are using a water bladder to carry water, load it at the very top of the pack. Make sure it’s sealed correctly! You don’t want water leaking all over your pack contents, which could be a disaster. Don’t try to pack a water bladder under other items in your pack. The weight will compress the bladder and can cause leaks.
The Side Compartments
Some packs have side compartments. These are natural places to store things like extra water bottles, water filters, first aid kits, fuel bottles, etc. Don’t place anything too fragile in the side compartments, as they get banged around a lot.
The “lid” of the backpack (sometimes called a “brain”) is a flap attached to the main body of the backpack with adjustable straps. The lid flips over the top of the pack to cover it and prevent rain and other things from getting in the pack. The lid usually has quite a bit of storage space as well, with one or two large zippered compartments. These compartments are a good place to store maps, compasses, fire starting material, first aid, knives, and other utility items.
Packing The Tent
The tent is usually bigger than all the other equipment, and it doesn’t easily fit inside the backpack. The tent can be strapped to the back, side, or bottom of the pack. Putting it on the bottom of the pack will make it harder to set the pack down on the ground. Another option is to put the tent on top of the main compartment before flipping the lid over the top. The tent is then held tightly on the top of the pack by the lid and lid straps.