In all of the planning discussions packs and bags are brought up a lot. The type of bag and the contents are discussed at length. Rarely though do you see a good discussion of PACKING the bag. Anyone that has carried a pack for any length of time can tell you that things needs to be organized in a particular way to carry it comfortably.
An often recommended way is to divide the pack into 3 sections. Gear should be packed based on weight, bulkiness, and how frequently it is used.
The Bottom Section
Bulky items that are needed less frequently should be placed here. Things like sleeping bags, sleeping pads, and extra layers for occasional use are some examples. These are light and can provide some cushion to carry the load of the heavier items.
The Middle Section
This section should be reserved for heavy gear that you do not need immediate access to. Cooking kits, stove, fire kit, crank emergency radio, and your main food supply generally fall into this. If you have a larger store of water, it should go here too. Just wrap in in some soft items to prevent it from being damaged by other heavy gear. Placing the heavy items in the center helps to keep it from tipping back or sagging down on you. Either will cause you to have to work harder without a stable center of gravity.
The Top Section
This section should be reserved for items that you need quickly or more often. Rain gear, first-aid kit, water filter, and toilet paper. For the most part it should be lighter items to keep the pack stable.
These pockets should also be used for quick access items. They will be smaller items and based on pocket location should also follow the same weight pattern as the interior. Items that fit this could be your compass, map, pack rain cover, sunglasses, headlamp/flashlight, water bottle, snacks, and hand sanitizer. Not only will this help you get to these items quicker, it will prevent them from being lost in the interior shuffle.
Many packs built for hiking or tactical use feature lashing points at different areas. These can be used to affix tent poles, hiking sticks, axes, or machetes. Some even have points at the bottom designed to be used for a sleeping bag or pad. Just be sure things are lashed so as to not swing around.
What not to pack iN your pack
There are some things I advise to not put in your pack. These would be personal documents, ID, at least part of your cash, your main knife, a flashlight, and basic fire kit. In addition if you carry a handgun it should not be buried in your pack. The reason these should not be packed, but on your person, is that a point could arise that you must ditch your pack. You may need to flee from danger, it might be taken from you, you may lose it in a water crossing, or many other scenarios. In these cases you need these very important items on you so that there is less chance of losing them completely.
It is important to test out the packing plan of your pack and how it carries. This will give you a chance to rearrange and perfect your load. Better to do it now than when your safety depends on it.