First, be cock-sure in your own ability to do something as simple and straightforward as identifying mushroom species because of your innate ability to recall every minutia of the field guides and your astonishing powers of perception and attention to detail. Then analyze closely the cap shape, scales, the gill/teeth/ridges/pore patterns in the cap underside including shape, width, spacing, depth, and color, the ridges, and the stalk, including a partial veil and/or annulus. Proclaim confidently when you have determined with 100% assurance that you know precisely what species of mushroom you have in your hand, because you are a mushroom genius.
At that point you can take a few bites. If you end up needing a liver transplant, then you know it was toxic.
Spore prints can be a huge help in identifying also!
There are some mushrooms that have very few known lookalikes (varies by geo/region), which have a handful of strong identifying factors. Morels, oysters, and a few others come to mind, where if you can confidently confirm these factors, you can be reasonably sure that you’ve identified them correctly.
That said, people sometimes convince themselves of these factors, especially when they haven’t had much experience identifying them before.
I do know a number of members of the IMA that have been there longer than me, and don’t forage at all!
At that point you can take a few bites. If you end up needing a liver transplant, then you know it was toxic.