Stepping into an unfamiliar barbershop should be a fairly straightforward interaction—you have gotten your hair cut before. But here’s where things get tricky: you’re sitting in the chair and the barber asks if you want a skin fade with a shape-up. Or a tapered high and tight. He wants to know what number you want. Suddenly, you regret not going to your regular guy before heading home for the holidays. To be sure, these conversations can get confusing, but once you’ve mastered the art of speaking barber, you’ll never worry about a tonsorial tragedy again. We asked Mr. B, of Frank’s Chop Shop, a Lower East Side institution, to walk us through time-tested styles, telling your ones from your fours—and most important, what not to say when settling into a new chair.

Stick to the classics.
Don’t expect the same personalized cut you get from your normal guy; instead, try a time-tested standard. There’s the gentleman, with clean, natural lines that can be parted or brushed back (think Don Draper); the shape-up, or fade, a buzz cut that’s blended up from the bottom and cut short at the front, following the hairline (think rappers); the high and tight, a fade in which the hair is kept short up to the widow’s peak (think soldiers); and the shag, a long, texturized cut (think Julian Casablancas).

Cut to fit.
Once you pick a style, tweak it to match your regular look, says Mr. B. Ask for it a little shorter or longer, a little more blended or texturized. Say something like, “Keep it high and tight—but not like I’m shipping off to basic.”

Chin up.
Getting a haircut is one of the few times a guy can stare at himself for a half hour and not appear vain. Mr. B advises, “Keep your head up, and look in the mirror. You’re going to get a better cut because it’s a better perspective for the barber.”

By the numbers.
What’s yours? No. 4 clippers leave your hair a half inch long; a three leaves it 3/8ths of an inch; a two trims it to a quarter inch; and a one puts it at 1/16th. Zero? You’re seeing skin.

Paint a picture.
It might sound obvious, but if you don’t think you can articulate what you want, show your barber a picture of a guy whose hair you like. “The best thing a guy can do is bring in a magazine or photo for a point of reference,” says Mr. B.

The right stuff.
“I don’t like when people come in and they have a ‘gelmet’—a helmet of gel,” says Mr. B. The day of your cut, don’t use—or go light on—product. Then ask for a water-based pomade, not one that’s alcohol based, because it dries your hair out.

Be your own man.
“This might sound harsh,” Mr. B says, “but I really get annoyed when a guy has his girlfriend or wife choose his haircut. Come on. How long have you been getting your haircut?”