How do I tell if a mushroom is poisonous?

Without eating it and taking a gamble

With experience, you can identify mushrooms by taste.  Take a little nibble, but do not swallow.  Chew for a little while.  Are your lips a little numb?  That could mean poison.  In that case, spit out the mushroom and rinse out your mouth well; it pays to be cautious about these things.

Give it some kid and watch closely.

NUMBER 2-- great advise.

bitterness is a sign of bad food that should not be consumed,also the spores also shows how toxic it is. there are many types of wild mushrooms that are flavorful. even thought todays market of mushrooms are most appeal towards vegens, health life, asian foods, and eastern European countries.

most mushrooms that are pale white caps as well as brown tops are less likely to be poisoness than colorful ones.

but for real, dont try something that is not worth suffering