One thing you need to be aware of is where you are harvesting the wild edibles. As most of the population (US anyway) lives in urban or at least suburban environments -- its important to be aware of what possibly toxic substances that tasty treat may have absorbed from its immediate environment. Circumstances like how close to traffic, what kind of run-off exposure, proximity of potential pesticides (say that 5 times fast!), and any soil contamination. Keep in mind that many urban parks and green spaces are there because they are covering over toxic areas that are too dangerous to build houses on. Its back to the same fundamental idea of survival: be aware of what's around you. That wild-salad is just not worth it if you have to follow it up with an activated-charcoal chaser.