My friend would like a facial parisian style while we are in Paris this September. Any recommendations?
You have to reserve well in advance, and they are expensive for what you get. They are basically the same thing you will get anywhere you live, but maybe with different products.
It is not required to tip the estheticienne.
Here's one in the Marais:
http://www.decleor.fr/institut-paris-marais
And one on the Champs-Elysees:
https://www.guerlain.com/fr/fr-fr/spa
I had an excellent facial at Carita at 11 Rue du Faubourg Saint-Honoré in 2013.