I forage, JRM. There's a really good book I use, called "Edible and Useful plants of Texas and the Southwest" by Delena Tull. You may find it useful as well.
Here in our little piece of paradise, I have harvested agarita berries, wild tomatillos, nopalitos and prickly pears, yucca petals and wild lettucesfor salads, and lots of mustang grapes, among other things.
I agree, it's absolutely vital to KNOW what you're looking at. The wild tomatillo, for instance, is related to tomatoes, eggplant and peppers, and also to deadly nightshade and several other poisonous plants native to my area. So, yeah, I want to know FOR SURE which member of the family I'm dealing with.
I also think it's crucial to harvest respectfully. I never harvest more than about 1/3 of a colony of plants (much less if they are scarce) and I try to return seeds and compost to the colony too.