What should you observe on a mushroom?

MycoWiki answer

Begin by describing the specimen without assigning a name. Observe the cap's shape, surface and colours, then the underside, the complete stem and its base. Record how many specimens are present, how they grow, their size, any visible change from handling or cutting only when a reliable guide calls for it, and the nearby trees, substrate and habitat. Photograph several stages if they occur naturally together. Clearly separate a feature you observed from information that is missing or uncertain. Only then consult a guide suited to the group and look for contradictions before similarities.