I remember my first and only visit to a parlour.
I was talked into it by a lady on the board as kind of a "I dare you" thing. lol
Paid the door fee and had a great time. She only asked for the door fee.
At end of the session I basically emptied my wallet then apologized i didn't have any more.
She got an $80 tip on a half hour massage.
Some girls have an "expected amount" and will tell you if you ask.
You also need to consider;
1. How much fun you had
2. How much work she put into it
3. Her attitude
4. How do you want her to remember you, if you come back.
I tell everyone to always mention it's your first time when visiting a parlour, indy massage or paid companion. That way they can guide you a little bit and won't get upset if you mess up normal etiquette.