As others have said sleeping system, shelter, and pack are great places to start. I did exactly that withmy36 lb load and brought it down to 26.
The next thing to consider is your kitchen. It is easy to have too much kitchen stuff. Your decision about water filtration, chemicals, UV, or boiling and whether you use alcohol, butane, or wood all involve trade offs that you should consider.
Finally, avoid hauling extra trinkets and electronic gadgets. Your phone, camera, gps, spare batteries, charging equipment, spare flashlight are heavy and they add up fast. An extra knife isn’t required, etc. Multiuse items are the key and your contingency items should find other useful roles.
a coupla thoughts on the CDT comments (I tried to answer down there, but got error message)
I believe the base weight refers to everything in your pack, not just 'the big 3', but minus food/water, as a base weight of 15lbs of just pack/tent/sleeping stuff is off. (example Osprey exos 2.5lbs, zpacks duplex 1.5lbs, 20F bag/quilt 2lbs) so the big 3 would be 5-8lbs (?) does that sound right?
Also, I find many people bring too many clothes. I recommend one set of clothes to hike in - EVERY DAY and then something to change into when and if those become wet when at camp; presumes putting the wet clothes back on each day and hike until dry/warm. Bring some extra socks and wash as necessary. Don't try this in winter.
I've struggled with lightening my load for years. The biggest culprits for adding to pack weight for me are:
- Redundant items or items that don't serve multiple purposes
- Too much clothing - I carry an extra shirt, bra, and a pair of shorts, in addition to my hiking shirt and pants, that I'll usually wear when I have to do laundry. I probably will ditch those this year and maybe just walk around naked when doing laundry. 😉 just kidding
- Too much food - I always think I'll end up starving to death if we have to take an extra on-trail zero-day or if something happens. Also, I've doubled up on portions just to get the calories needed. I've since scaled down the portions to singles and stopped carrying too much extra food. I still pack a little bit for an emergency, but I don't go overboard now. I was actually hungry (ok, starving) this past year on the PCT. This one is difficult to balance what you actually need. I do repackage my food into Ziplocs though to save weight (and space); the packaging for freeze-dried/dehydrated meals adds up.
- Comfort Items - Things that I could really do without, but still don't feel comfortable ditching, like my overloaded first-aid kit.