The Fey keep their promises, always.
"'It is one of our most stringent laws,' I said. 'To be foresworn is to be outcast.'"Merry Gentry, 'A Caress Of Twilight'
The sidhe never lie, ever. "It has the kernel of truth, or it would be an outright lie, and we do not lie to each other."Doyle speaking to Merry, 'Seduced By Moonlight' But evasion, and partial truths are absolutely fine, in fact, using them has been turned into an art form. "Maybe, but a sidhe will omit so much of a truth that it might as well be a lie,"Merry replying to Doyle, 'Seduced By Moonlight' "The sidhe never lie, Meredith, but shading the truth is a long-honored pastime among us."Frost, 'A Caress Of Twilight'
You never take either food or drink from a fey unless you are sure they mean you no farm,not particuarly because it might be poisoned, but because it might be bespelled.
"... but it was a rule that you never took food or drink from a fellow fey until you were sure they meant you no harm. It wasn't poison you had to worry about, but spells, a little potion mixed in with the lemons."Merry Gentry, 'A Caress Of Twilight'
"Among the fey it was impolite to ask why a person was having hysterics. Hell, sometimes it was considered impolite to notice that they were having hysterics at all. Usually that was for ruling royalty though."Merry Gentry, 'A Caress Of Twilight'
It is incredibly bad-mannered to ask a fey a personal question if he/she has not first given their permission.
"and didn't understand that among the fey a personal question is the worst insult."Merry Gentry, 'A Caress Of Twilight'
Fertility in a fey is held in high esteem.
"Children are precious, and anything that breeds, that passes the blood along, is worth keeping around."Merry Gentry, 'A Kiss Of Shadows'
"It wasn't personal, but among the fey it's an insult to ignore someone who's obviously trying to be attractive"- - - "You're always supposed to say something nice the first time you see someone in a state of undress."Merry Gentry, 'A Kiss Of Shadows'
"It was an insult to insist on modesty in a nonsexual situation among most of the fey, certainly among the sidhe.---To send them away would imply lack of trust, or outward dislike."Merry Gentry, 'A Kiss Of Shadows'
"Nude didn't mean sex to the sidhe, not always."Merry Gentry, 'A Caress Of Twilight'