You can either describe what you want, or show a picture of a haircut that you like.

I tend to bring a picture or two of the style I want.

“I dunno. I suck at this. what do you think?”

don’t do that at the cheap joints… but otherwise it usually sets up a good discussion.

protip, if you’re wanting a men’s style… go to a barber. usually less expensive, and usually much better at men’s style. (Also, most barbers don’t care if your a man or woman or non binary. they still won’t charge you extra the same way a stylist will charge some one passing as a woman women’s rates for the same thing. it’s pretty absurd.)

I throw up some confusing explanation with gestures before my barber does the same haircut they did to me for 5+ something years. Idk what would I do if they retire.

I usually just show a picture because I never know what the styles are called, I just know I want it on my head.

“Like it is now…only shorter.”

Describe it however you want. If you have a decent barber, they should understand you fine and work with you.
I’ve been shy, straight forward, and all manners of sides when asking for a haircut and the biggest issue has only been the occasional language barrier.

Once you’re comfortable in a style it’ll be easier to use different wording, depending on how you want your style. For example: you most certainly can ask for clipper sizes, like “no. 2 on sides”, however if you don’t know what you want from the top you could just ask them “a bit short but matching the sides, if you know what I mean?”

Some styles have different options, such as skin fades (usually medium or high here, indicating the point where the fade reaches on the side and back of the head). If you’re unsure definitely do not be afraid of asking, if any barber has an issue with working with you they aren’t the barbers you want as they’re likely to rush the haircut regardless of what you say (in my experience), or only know limited styles/lack broader experience in hairdressing.

I bring a picture of myself with the haircut I want.

Husband says tight fade, zero to very short on top and that gets him what he wants, he goes to the same barber lady all the time, she doesn’t speak English and he doesn’t speak Spanish but they still manage to communicate the haircut information.

“One haircut, please.”

If they’re good at their job, you can ask pretty much anything and they’ll ask follow-up questions. If not they’ll infer what to do or do one of the standard haircuts.

I show my hairdresser a picture of my previous haircut (or one I like).

“the usual”, because i don’t know what hairstyle fit me and don’t know what its called. I tend to ask what hairstyle fit me and then get the same haircut everytime.

i show them a picture of my cock. please make my head look like this.

I say: make my hair beautiful/better (in the local language). I don’t really need to do anything else, it seems to work.