1. Research your destination to find out what you really need. Check average high and low temperatures, typical weather patterns, water sources, and the short-term forecast–then pack for those conditions. Lots of water available? Take fewer bottles. Warm weather predicted? Leave the extra layer at home. Berries in season? Reduce your food load.
2. Make your gear do double duty. Get a tent that pitches with trekking poles. Use a bandana as a towel or pot holder, extra socks as gloves, a long-sleeve shirt as a scarf, and a bear canister for a camp chair. And don't double up: Pack a windshell or rainshell, but not both.
3. Don't overload on clothing. On most fair-weather hikes, this is all you need: pants, wicking T-shirt, long-sleeve midlayer, two pairs of socks and underwear, sun hat, warm hat, light gloves, and a rainshell (approximate total weight: 3.5 lbs.). If you expect cooler temperatures, add long underwear bottoms and a lightweight puffy jacket. Hiking will keep you warm during the day, and your bag will do the job in camp.