Hmm, never thank the Fair Folk. Saying "thank you" implies they did something for you. It puts you in their debt. Real or not it becomes real when you accept it by saying "thank you". Instead you can show gratitude by complimenting the service or item eg.. "The coffee here is always the best" etc...
Never, never, never receive anything before you pay. Pay first, then take your items. Also be sure they actually tell you the cost. Just because it's on a sign doesn't mean that that is its price. In the mortal world where there's a sales tax makes this easier because most people can't figure out the total.
Bonus: If you personally hand them a tip and they accept, that puts them in your debt. That's why there's a tip jar. If you choose to leave your money in the jar that's your prerogative, but if they take it from you it becomes a gift from you to them.
Never, never, never receive anything before you pay. Pay first, then take your items. Also be sure they actually tell you the cost. Just because it's on a sign doesn't mean that that is its price. In the mortal world where there's a sales tax makes this easier because most people can't figure out the total.
Bonus: If you personally hand them a tip and they accept, that puts them in your debt. That's why there's a tip jar. If you choose to leave your money in the jar that's your prerogative, but if they take it from you it becomes a gift from you to them.