I would observe what the local animals seem to be eating.
Another trick is to take a sample and rub a bit of it on of your skin. If it causes irritation, its probably bad.
I would observe what the local animals seem to be eating.
Another trick is to take a sample and rub a bit of it on of your skin. If it causes irritation, its probably bad.
If you're able to find enough edible plants (via watching other animals), it might also be worth trying to cultivate them, but this depends on your broader circumstances.
Apparently blood and alcohol are also bad. They are processed as food, which requires large amounts of water from your body. Thus while they're both fluids, they result in a net loss of water.
Fish apparently have a column of fresh water near their spine. You can cut them open and drink from this. You can also suck fresh water from their eyes.
Edit: Oh, hey, a citation:
http://en.wikipedia.org/wiki/Urophagia#Attempting_survival
Everything else is from "Complete Survival Manual," Michael Sweeney.