You: I'm going to tell you the same thing I've told you since I was twelve because I don't really know anything about hair.
Barber: That's okay, if I do something different, you wouldn't be able to tell anyway.
You: Sounds good.
Barber: Now I'll just inaudibly mumble something that sounds like it's probably a joke.
You: Hahaha! I sure am trapped in this chair.
Barber: Does THIS look like a good length?
You: I can't judge what a haircut will look like based on the tiny amount of hair your pinching between your fingers so I'll just assume you know what you're doing.
You: There's hair all over my face, but for some reason it seems rude to ask you to brush it off. I'll just sit here and contemplate the nature of itching and self-control.
Barber: Now I'll show you the back of your head. How does this look?
You: That is literally the one part of my body I never look at. I don't care how it looks.
Barber: Good. Do you want any gel?
You: I'm going to panic and say "yes" for no reason.
Barber: There. What do you think?
You: It doesn't matter because it's too late to change anything. Here's a random amount of money that I think is an appropriate tip.
Barber: Thank you! Be sure to check your head in every reflective surface on the way home.
You: I will!
Friend: Hey, I'm going to tell you I like your haircut so you'll think I'm perceptive.
You: Thanks! That's what everyone else is doing too!