First buy a Backpack that can be adjusted for your torso length and also hold the items you intend to be carrying. Determine your torso length by measuring from the base of your neck, or seventh vertebrae, down to your waist. The shoulder straps should attach to the pack a tiny bit below your shoulders, not above or to low below the shoulders.
Now load your backpack with all the gear and supplies that you’ll be using, or some sort of realistic load. Put your sleeping bag at the bottom of the pack so that nothing heavy is pressing or bouncing against your lower back. Put the heaviest items close to the back and centered in the pack. Make sure heavy items are secure and not flopping around. Place your smaller items near the top where they can be easily accessible on the trail.
Next loosen the hip stabilizer straps, hip belt and shoulder straps before putting on the backpack. Slip one arm through the shoulder strap, then reach back with that arm and move the bottom of your pack to position it in the center of your back, while leaning forward slip the other arm through.
With pack on, slip the shoulder straps over your shoulders and secure the hip belt with the buckle in the center of your waist, tighten snug. The hip belt should lie over the hipbones and not above over the stomach because it may constrict your stomach. The hip belt should carry most of the load.
Now draw down on your top shoulder straps until they are just snug, but not overly tight, unless you're climbing up or down a very steep incline. There should be no pinching on the armpits or excessive pressure that could cut off circulation. You might have to adjust the lower shoulder straps too. Next tighten the hip stabilizer straps so that the pack is snug against your lower back. Next position the sternum strap to a comfortable location that is not overly tight.
The backpack should be snug against your body and balanced so that the weight is distributed evenly over the shoulders and hips. A pack being too lose may cause unwanted pressure to be focused on a particular part of the body.
Each backpack and person is different. Internal frame or external frame. So you will have to play around with your adjustments to see which one will work best for you that fits your particular body type and type of pack.
Remember that comfort is very important especially on long hikes. There's no need to have unnecessary discomfort or risk possible injury. It's a good idea to take some short hikes before your adventure so you can feel the weight of your full pack and also make sure that it's adjusted properly. You'll learn very quickly not to overload your pack, so choose your gear wisely.
The average hiker with a backpack can hike around 2 miles in an hour over flat terrain. An aggressive hiker can hike at speeds from 2.5 to 3.5 mph. Uphill or ascending up steep terrain the hiking speed averages 1 mile per hour. Downhill or descending down steep terrain the hiking speed averages 1.5 miles per hour. This will help give you a ruff estimate on how much time the hike is.
The average backpack usually weighs around 40lbs. Some of the items include tent, sleeping bag, sleeping pad, food, medical kit, food preparation gear, rain poncho, flash light, water proof matches, water bottles and a water purifier to name a few. The average hiker usually carries around a half gallon or 2 quarts of water which weighs 4.17 lbs., which is good for about 4 hours of hiking, so knowing where to replenish your water on longer hikes or multi day hikes is very important.