rule #0 of picking mushrooms is NEVER eat a mushroom unless you are 100% positive about its identification. become familiar with the terminology that mycologists use to describe mushrooms (pileus, stipe, annular zone, spore print, fibrous, etc etc)
rule #1 of picking mushrooms is ALWAYS use a separate container for each type of mushroom that you find, and ALWAYS label the container with detailed notes about the habitat
rule #2 is know what you are looking for before you go out, and read your field guide (you do have a field guide right?) thoroughly so you know what to expect.
different species of fungi have different habitats. some are parasitic on living trees. others are saprobic on dead woody debris. others are dung-lovers. still others gain their nutrition from a symbiotic relationship with plant roots. there are even fungi that infect and eat insects (cordyceps). knowing what your mushroom should be eating is a large step to identifying the fungus.
know your seasons-- some fungi fruit only in cold weather, others like it warm. in general most will only show up after a good rain though, so don't go hunting in the middle of a drought cuz you won't find jack shit.
mushroom hunting is only about 100x more complicated than "is it active or not" unless you are fortunate enough to have someone show you the ropes first-hand. an internet photo of a mushroom is NOT sufficient identification to consume.
