Anyone wishing to collect wild mushrooms should do so with an experienced guide or join a local mushroom club. They should also get several guides - starting with the "National Audubon Society Field Guide to North American Mushrooms". An example of couple of other books that one may want are: "North American Mushrooms: A Field Guide To Edible And Inedible Fungi", by Orson K. Miller, and Hope Miller, and a more localized book like, "Mushrooms of Northeast North America", by George Barron.
Learn the choice edibles and the most poisonous mushrooms like the Death Angel and the Deadly Galerina. In general, stay away from mushrooms in the Amanita family of fungi even though there are some edible varieties here, and small brown gilled mushrooms.
Introduce yourself slowly to mushroom hunting.
Never eat more than a sample portion of a new-to-you mushroom.
Above all, always be very attentive, to details, smells and what the mushroom is growing on - for example, soil or wood.