Edibility

This is a Chlorophyllum molybdites, the vomiter, it won't kill you, but you'll wish it did.

1. How to avoid poisoning

Eating foraged mushrooms is a time-honored tradition across the globe. However mycophobia is present in a lot of cultures, including here in the South-East US. But if we can safely identify toxic mushrooms and rule them out, we're on our way to having access to the loftiest realms of culinary ingredients.
While there are SOME ways to detoxify certain mushrooms, we're going to avoid that and just focus on safety.

Cortinarius sp. See the rust-colored fibers on the stipe?

What to avoid, unless you're an expert

For identification beginners, or intermediate folks, we strongly suggest you avoid the following genera:
Amanita (mushrooms with white gills, a skirt or ring on the stem and a bulbous or sack like base called a volva), Chlorophyllum (green gills and spores, commonly found in fields), Cortinarius (will contain a fibrous cortina attaching the cap edges to the stipe in young specimens, these are often confused with Blewits [Clitocybe nuda]), Gyromitra sp. (which look like little brains and are considered one of the morel 'look-a-likes'). Omphalotus sp. (the Jack-o-lantern mushrooms are commonly confused with Cantharellus [chanterelles]). There are many more that could make this list, but these are some of the most common.
And of course, don't eat ANYTHING unless you are 100% certain of it's identification.

This is a young Omphalotus illudens that sure does look a LOT like a chanterelle from above.

Old wives tales, we should avoid those

There are a lot of "old wives tales" regarding the edibility of mushrooms. Avoid these. These tales are often region-specific and unscientific.
An example is that we can eat any mushroom that an animal like a squirrel can eat. FALSE. Squirrels have evolved several enzymes to break down some of the most toxic mushrooms to humans. This false information could easily lead someone to consume a deadly-toxic mushroom that may not have been present in the region the lore was created.
When taking your health into your own hands, confident identification to the Genus and species level is Critical. When in doubt, throw it out.

Edibility testing

2. So we've identified a mushroom and it's not poisinous, now what?

Is the mushroom woody, leathery, or corky? If so, why would you eat it?
Is it moldy or mushy? Don't eat it. Only eat prime mushrooms. Anything past it's prime should either not be eaten, or in some cases, may be dried to use as seasoning.
Please note that almost all mushrooms require cooking to be safely consumed. This is due to the make-up of the cell walls of most fungus actually being indigestible to humans, unless its been cooked.

Got a mushroom that's new to you, but supposedly edible?

 When trying new species of fungi with unknown edibility or when venturing into new genus we have one way to mitigate toxic effects or even allergies. This is called the Leather's edibility test and is  available in my Alma Mater mushroom club’s website.  The gist of it is to first and foremost be very confident in your ID, at least 100% confidence in the Genus (you really don’t want to mix up Agaricus bisporus with something like Amanita phalloides which can kill you quite painfully and getting to genus ID may inform you that there are no/some/all toxic species within the genus).  You start by COOKING and eating a VERY SMALL amount, the size of a piece of rice for questionable genus and perhaps a bit larger if you are working in a genus that has no known toxic species. Wait 6-8 hours. If there is no effect, try a teaspoon’s worth, and wait 6-8 hours. Waiting for this period of time is important because many fungal toxins  take time to do their damage. In fact, amatoxins take about 24-36 hours to show an effect, so give it more time if you suspect the genus you're tasting may contain any toxins. Waiting an appropriate period of time,  cooking all (sans a small list) wild mushrooms, and slowly working your  way to larger volumes, should allow any serious mycophile to try many,  many new and exciting mushrooms! This test helped me venture, fairly comfortably, into eating - and  really loving - edible Amanita species (following the successful identification and mycophagy of several safer genera and waiting 36+ hours after the first taste).  If you are new to wild mycophagy (the eating of fungus!) please give  this method a shot as non-toxic compounds can still produce ill- and  allergic-effects. I want everyone to be able to try new species and  figure out which of the thousands of fruiting fungi you like best, with  confidence.  

Still questionable?

If you're not sure about this method we suggest speaking with an expert and discussing your concerns. When in doubt, throw it out.