How to Lighten Your Pack for a Backpacking Trek

Your pack looks perfect; every strap is tight, it is balanced, nothing is jabbing your back, it looks just like the poster at REI. The only problem is getting this 70 lb. monstrosity on to your back! Here are some tips for shaving weight off of your backpack without sacrificing any creature comforts.

Steps

1. 1 Do not pack any canned foods. Plan your menu without cans, the metal is heavy, they are full of water and you have to hike them out. It is easier than ever now that tuna (a backpacking favorite) is packaged in vacuum sealed bags instead of cans. Between mountain house and other dehydrated foods, and grocery/ health foods stores selling bulk dry grains and fruit, there is no reason to carry cans.
2. 2 Share the load. Divide a 2-3 person tent into poles, tent, and fly (or whatever is even). Split up the stove, fuel and cookware. Only pack one water filter per 3-4 people. Does everybody need their own GPS, big survival knife or Leatherman tool? How about just one per group.
3. 3 Use trekking poles or a hiking stick. This won't make your pack any lighter, but it can shift 15-30 lbs. from your legs/feet to your arms.
4. 4 Pack seasonably and sensibly. If you're planning for summer, or a hot climate consider purchasing a +40f rated bag, or just a light fleece blanket and leave the -15f down at home. For spring/fall when the temperature can drop from a seemingly sunny day, bring a wool hat, it is lighter and warmer than another layer. Buy a comfortable and breathable rain jacket you can wear as an extra layer.
5. 5 Don't believe that expensive/ high tech is necessarily lighter or better. Titanium cookware despite its durability and super-coolness, can be the same or heaver than its aluminum or lexan counterparts. Nalgene and Kleen canteen brand bottles come in fashionable colors but are significantly heavier (and not necessarily more durable) than disposable plastic water bottles. Even the lightest Thermarest inflatable pad is heavier than the heaviest z-rest or ridgerest foam pad.  
6. 6 Get the right shoes. Shoes are a balancing act, too light and you risk injury, too heavy and they can feel unnatural and tire you out. If you are carrying a heavy load and need full ankle boots, consider synthetic materials rather than full leather, and never ever use steel toed or steel shank boots. If your pack is under 1/4 of your body weight, or you feel comfortable and experienced enough, low top boots or trail running shoes are a great alternative. They are as tough as full boots but much lighter (while sacrificing some ankle support). They say an ounce on the feet is a pound on the back.
7. 7 Fuel. While many of us would love to carry nothing but a flint to cook with, few national forest or parks allow wood gathering, and those that do have restrictions (high altitude, burn bans) which can prevent use of firewood as a dependable fuel source. So use your fuel wisely. I love to cook with grains, beans when i backpack, but dry lentils and plain rice can take 20-30 minutes worth of gas. Instead use dehydrated beans and instant rice, which take a little over 5 minutes. Also, iodine tablets or a UV sterilizer is lighter than the fuel it takes to boil as much water. Don't forget your wind-shield.
8. 8 Pack the right clothes. Extra socks are a no brainer, but any clothes not planned for layering are not needed. If you're wet and risking hypothermia, time to get in the sleeping bag. A dry sweater can only do so much. Wash your clothes in a stream (not as good as a machine with stain fighter and downy, but it still feels really good).
9. 9 Avoid cotton. Synthetic (Coolmax, Duofold, under armor) in the summer. Wool and silk in the winter.
10. 10 Dual purpose. Rain gear as an extra layer. Eat and cook with the same utensil. Use a space blanket as a ground cloth. Trekking poles as rain fly poles. Pot as washbasin. Pill divider as spice rack. the list goes on and on.
11. 11 Upgrade. So, you've weeded out every extraneous milligram from your pack, and you still want to go lighter? Time to bust out the wallet. A big weight factor is the pack itself. Gregory, Patagonia, and Dana Designs all make "ultralight" backpacks. These are different from typical frame backpacks in that they use silicon impregnated nylon (same stuff as hot air balloons and stunt parachutes) instead of heavy-duty nylon and have a carbon fiber, aircraft aluminum, or no frame at all. Some tent companies offer aircraft or carbon fiber pole upgrades from their heavier fiberglass or aluminum stock poles.