I tip beforehand and generally get great service doing that, if I don’t get good service I won’t go back.
This is the way i look at. I’d rather get burned on a tip then get subpar service and not leave a tip after it’s over. If the service is terrible you won’t go back anyway.
I remeber one time i set an appointment at a place I was new too, and they stuck me with some old saggy lady. On the flip I told her I was done and put my clothes on and left. She tried to give me back my money and I told her no. On my way out, a younger woman chased me down and pulled me back into the room, apologised and gave me a great long session.
I still never went back.