Here's my packing list for outdoor trips. I try to store all of this stuff in my walking pack. The things that I store outside the pack for any reason are on a list that lives inside the pack. This makes the process of packing for a trip fairly easy: tip everything out on the floor and sort everything into a "take" pile and a "stay" pile. Inevitably the "take" pile needs a few more culls before it's down to a reasonable size.

For walking trips, I pack everything that I can't afford to lose inside the pack. I once lost the poles from a tent I borrowed from a friend halfway up a cliff in the Budawangs - never again. Get a big pack. If you have to put your pack on a plane, get a large sack to put it in first. This will stop all the buckles and straps getting caught in the baggage handling machinery. I have a large ripstop nylon bag that I bought from a local outdoor gear manufacturer designed specifically for this purpose.

• Water bottles/bladders. Allow for up to 6 litres capacity. As a general rule I start a walk with at least 2 litres.
• Food. Allocate 800g-900g of dry weight food per day. Avoid food that has a high moisture content. No pumpkins!
• Sleeping bag. If you've got a down bag and it doesn't seem to be as warm as it used to be, wash it carefully in a bathtub with approved down soap. Store it unstuffed in a large bag.
• Inner sheet/bag - keeps your sleeping bag clean and you a little bit warmer. You can also use it as a bag to store your lofted sleeping bag in
• Sleeping mat. I use a 3/4 self-inflating mat and a 1m length of foam mat for my feet and legs. I use the foam mat for sitting on during the day and around the campsite, and if the self-inflating mat should develop a leak, I can use it as a backup main sleeping mat
• Tent. Freestanding is good
• Fuel stove. If you're flying, check exactly what you're allowed to pack - the airline may not be happy with empty fuel bottles that may contain flammable vapor.
• Matches and cigarette lighters. On airlines I think you are only allowed to carry these on your person.
• Fuel. Once again, this is a problem on planes - I don't think you can take anything. Make sure you can get the required fuel at the other end, and if you're flying overseas, find out what it's called in the local language.
• Spoon
• Mug
• Bowl. Optional if you can eat out of the stove(s)
• dish sponge
• Rain jacket. Will keep you warm too.
• Waterproof overpants - optional. Sometimes I just take a a pair of thick stretchy ski-pants, a bit like the bottom half of a wetsuit.
• Warm clothes - thermal underwear, fleece/down jacket, beanie
• Hat. Mainly to keep the sun off, but is also good at deflecting eye-level sticks if you're scrub-bashing. Something collapsible with a wide brim is good.
• Walking boots
• First aid kit. Include a compression bandage for snake bite and know how to use it.
• Clothes. You'll often want to keep the sun off, so long sleeves and collars are good
• Sunscreen
• Pen/Swiss-army knife
• Toilet spade
• Toilet paper
• Maps, track notes
• Compass, maybe GPS too
• Personal Locator Beacon (PLB)
• Pack towel
• Repair kit - cable ties, needle and thread, some gaffa tape, spare pack-buckle and some webbing, MacGyver brain-dump ...
• Small inflatable pillow. Weighs nothing, cost $2.50
• Water purification tablets or device
• Pack liner. I line my pack with large plastic bags sold as outdoor garbage bags.
• Random selection of stuff bags, ziplock bags, plastic bags
• Toothbrush, toothpaste
• Gaiters - optional. Recommended for outback walks for spinifex protection.
• LED head torch and batteries
• Lip balm
• Pack-hauling rope - optional
• Thin cord to use as washing line
• Insect repellent - optional
• Sunglasses
• Camera - almost never optional

For cycling trips, add...

• Tools. A Swiss-army-knife-style multitool might cover most of this.
  • Allen keys
  • Puncture repair
  • Chain lube
  • Chain breaker
  • Screwdriver(s)
  • Tyre levers
  • Shifting spanner
• Spare inner tubes
• Water bottles