A couple things I like to do from what I have learned over the years:
Take, learn, and practice survival skills that are practical. Learn to make many things you might carry in. A bed, a meat pack, a shelter, and feel confident in your skills.
Get on a diet! If you are lean and on a solid, low food intake diet, you won't need weight in food, but high value and energy foods that you just eat as fuel. Of course water is a necessity as stated before. My hunting partners always are surprised at the energy I have, but it is because I prepare. It also means I carry less.
There's a book by Kochansky (sp?) on tips in the wilderness called Bush Craft that I really like. Some of it is more for dire situations, but there are a lot of good ideas. His class was great. Basically, learn to use what you carry and you will carry less.