This is a short extract from the book "Survival Advantage" by survival expert Andrew Lane. If you do not know what you are looking for, trying to identify edible mushrooms can be like a game of Russian roulette. Be sure you know what you are picking!
"Many old wives' tales are associated with fungi and most, if not all, are misleading and dangerous. Ignore them, no matter how much logic appears to be behind them or however convincing their source. Also, seeing that a fungus has already been nibbled is no proof of edibility. Many animals are capable of eating fungi which are poisonous to us. There are no shortcuts: you must learn to recognize their characteristics and be satisfied only with 100% correct identification before eating.
Fungi come in many shapes and sizes. It is a common mistake to believe that any small fungus you find will eventually grow into a big one. Many, even fully grown, are too small for us to bother about. Some are so tiny, they can only be seen properly with a hand -lens. Initially, concentrate your efforts on those fungi which grow to a worthwhile size. Identification relies heavily on visual features, but do not discount smell and, when you become more proficient, taste. Examine the fungi closely and you will observe great variation in detail between species.
Initially you will find yourself attracted by the colours of different species, but this in itself is not the only visible feature and, anyway, it is not entirely reliable. Differences in colour occur within species, varying with age and weather conditions. They can be washed out by rain or faded by sunlight...."
Survival Advantage by Andrew Lane.