Backpacker Magazine in its latest "Daily Tip" gives five ways to lighten your new pack.
Basically, they all make sense. But let's be a bit more critical in our thinking about lightening up. Backpacker's suggestions are listed first, my comments follow.
Backpacker: Remove your pack's aluminum stays. Better: don't buy a pack with aluminum stays.
Backpacker: Replace your rain cover with a Sea to Summit Ultra Sil Pack Liner at $45. Better: use a plastic trash bag in your pack to keep your gear dry.
Backpacker: Swap out thick bear-bagging rope for 50 feet of a thinner cord such as Kelty’s Triptease Lightline ($15; 1 oz.). Better: don't carry a rope, especially if you are carrying a required bear canister. Or, if you must some rope, cut it in half.
Backpacker: Remove the pack lid. Better: resist the urge to fill every space with gear. Take nothing that doesn't do double or triple duty, such as a bandana you can use for a napkin, wash cloth and filter to keep the big particles out of your water bottle.
Backpacker: Ditch your water bottles. A 3-liter bladder holds more water than two bottles, shrinks when empty, and makes staying hydrated much easier. Better: bladders are nice, but may not fit in your pack, and they often leak. Use a smaller bottle, especially when hiking in areas with lots of streams and lakes and fill up more often.
Be light. Be safe. Be one with the pack.