I learned as a kid that if you ever meet a handsome, well-dress and mysterious man at a party, you should check out his feet. El diablo might take the form of a handsome man, but he will still have una pata de chivo y una de gallo (one foot of a goat and the other as a rooster). Also, if he’s a musician, make sure that his guitar case is not full of snakes. That’s a bad sign too, as some great uncle found out long ago… or so the story goes.
El diablito: P√≥rtate bien cuatito, si no te lleva el coloradito. (Behave yourself so that the little red one doesn’t take you away.)