Plant identification mistakes are often forgiving — many similar-looking
plants are at least non-toxic, even if not the one you intended.
Mushroom identification mistakes can be far less forgiving.
A few reliable features matter more here than almost anywhere else
in foraging.

Turning a mushroom over and looking at its underside is one of
the most important identification steps. Does it have thin gills
radiating from the centre, small pores like a sponge,
or tiny tooth-like spines?

This single feature splits mushrooms into broad groups
and is essential for narrowing down what you're looking at.

Leaving a cap gill-side-down on paper overnight produces a spore print —
the colour of the spores that fall. This is a genuinely useful
identification technique, since spore colour varies meaningfully
between species that otherwise look quite similar.

Look closely at the stem (stipe) — is there a ring around it?
A bulbous base? A cup-like structure at the very bottom (volva)?
These features are critical, since some of the most dangerous
mushrooms have a distinctive base structure that's easy to miss
if you don't dig the whole mushroom out carefully.

Smell is a genuinely useful feature for many mushrooms —
some have distinctly fruity, almond-like, or unpleasant smells
that help with identification. Texture matters too:
slimy, dry, fibrous, or brittle flesh all narrow possibilities.

As covered in section 2.4, many mushrooms have specific
relationships with particular trees. Noticing what's growing
nearby — birch, spruce, pine — is a genuinely useful clue
and sometimes essential for confirming identification.