You can't...since witches don't exist.
england
Elizabeth Guant
brazil
Hansel and Gretel
yes the witch and the bottle is a Myth and also it comes from England
A Witch's companion is often a black cat, or a familiar. A familiar is a creature said to feed from a numb spot on the Witch where the blood doesn't flow. They are said to live on the witch on a mole or wart, that's why witches are often characterized with a wart on their nose.
You ask the person, very nicely, "Are you a witch?" If they reply yes, they may either be joking, or you may have found yourself a real life witch. If they reply no, then move on and pretend you didn't ask. There are no fool proof ways of "spotting" a witch.
If you are in England then you burned at the stake. If in the US then you where hanged.
London, England
Massachusetts.
1966
Two forms of evidence that New England courts recognized as proof that a person was a witch were spectral evidence and effluvia.