I have been reading some books by Andy McNab. He's a former British SAS guy that was held by Iraqis during the 1st Gulf War. The book that I am currently reading deals with his training or selection as he was trying to get into the Regiments. What I thought was cool was a blurb about what they were taught about foraging in the jungle. This would work anywhere Im sure. Note - I am aware that nothing beats real knowledge and taking a class or reading a book. This deals with when you have no alternative and the only other option is starvation.
His tip - take the berry (as an example) and rub it on your skin. If you dont have an allergic reaction (over a period of time), then rub it on your lips. No reaction? Rub on your tongue. No reaction > eat a small bit. No reaction > eat a bit more.
Just seemed like a really neat bit of thinking and if I told my wife this, she would give me the prepper wife look. You know the one I mean.