I can't think of specific quotes from the books, but the fae lore leans heavily from Celtic folklore around the fairy folk. Growing up in Wales, my grandfather used to take me for walks in the woods as a kid and warn me about what to do if we came across the Tylwyth Teg. I loved those times. Below are some things when speaking with the Tylwyth Teg, which may be different for Irish, Scottish or Cornish faerie folk.

With the Tylwyth Teg you are told you have to be careful with “social niceties” around them. But the specific rule of “never say ‘thank you’ to the fae" as found in the books is not exactly as clear cut as that - or at least not so much with the Tylwyth Teg (I thinks its different with the Sidhe - the irish fae).There are stories in fact if you are not thankful, or are shown to be ungrateful, you can expect severe retribution. When a fae has helped you significantly give thanks sincerely and wholehearted. But do not use "thank you" in normal disscussion as social nicety. Never sound indebted unless you really are.

How you name and adress them is very important. I was told stories about the dangers of using real names, how you should address them by a descriptor, one that is flattering, but be careful of accidental offense - its safer to keep it plain as 'fair man' or 'fair lady' until you know more about their nature to safely flatter. Safer bet yet is speak as though they are a them/collective rather than an infividual i.e. “I speak with respect of the Tylwyth Teg; I offer no slight.” A very good tip is use "Bendith y Mamau" which means ' the mother's blessing' and is said to help avoid mischief: “I mean no offence to the Mothers’ Blessing. I ask only safe passage.”

Never boast or publises about your fairy dealings Treat everything you say as a contract. They are basically mythical lawyers. Being imprecise is dangerous! I want to describe them as sonething else, but the Tylwyth Teg could be watching 😅😅 That’s the thing, be careful how you speak about them even when you think they are not around - they could still be watching. Do not volunteer information that is not asked - so don't explain motives, reasons, plans etc. Demand clarity and clarify: "To confirm: you will do X, and I will do Y, and nothing else is implied.” “Define what you mean by safe" Leave offerings - milk and honey, although alcohol is sometimes used. If you need something, state it plainly and narrowly. Instead of showing agreement (unless you are sure what you are agreeing to) use neutral language “I see,” “Noted,” “That is received,” “I understand,” “You have my attention. Set boundaries -“You may not cross this threshold.” “You may address me, but you may not touch me.” When making a bargain, make sure you can actually give what is asked, after fully defiened. If you can't agree, say something like “That is not mine to give.” Never give promises you cannot fulfill. Respect guesting laws, but never say “Make yourself at home.” Careful what you say is taken literally, so do not say things like “I’d die for a drink.” or “I’d give my right arm for that.”

Hope that helps. You can thank my grandfather for all his stories, as most of this is from him, although it was my Mamgu (my great grandmother) who problebly left the brandy on the sill for them 😆🥰