How do you know that the mushroom is a lobster mushroom?

Brown cap, gray white gills, and stout stem tell you that a mushroom that clusters along clearings and paths as well as in grass from June to October well may be the fried chicken mushroom...

A greasy, buff to ochre tan cap and clay brown gills on a basally enlarged, white stem tell that a mushroom that grows singly or in groups around clearings, on lawns or under trees from September to...

It will have a halo =)

they're fat and ugly

A mushroom that has spoiled will be slimy and smell of ammonia.