If possible, find some books on the ethnobotany of the plants native to your area and learn to identify them. Most books on survival I've seen cover uses of native plants. I learned quite a bit about local plants talking to my great-grandmother when I lived in Oklahoma. I still seek out the advice of the "old-timers" in the area I live in. Fortunately, much of that type of knowledge is being recorded in most areas. Have fun learning!