Go to a place that typically only serves men, so even if they don't agree with/don't like what you ask for they won't have alternatives in mind to push on you. I made the mistake of going to a regular place (serving men and women) once when early in transition and the lady ignored my instructions, cut my hair however she felt like, explained that I wouldn't "look pretty" with a men's cut, and then charged me like 60 dollars.
Later, when I was passing okay but had a kid calling me "mom" and "dad" interchangeably, I went to a men's barber and explained what I wanted. I told the guy I was trans and that I wanted to minimize my femininity, and gave him creative license to do whatever. I figured if he messed it up I could just give myself a mohawk or shave it all off. What he did was interesting and it worked well for me, basically a respectable short cut that you could wear to an office job, but cut shorter/thinner up near the corners of the forehead. I'm not sure how best to explain it and I wish I took before and after photos.
I don't pay for haircuts anymore, and probably wouldn't even if I had plenty of money. I keep my hair pretty short by feel with clippers. I use the longest setting on the top and a setting a few sizes down on the sides, paying special attention to keeping the hairline straight on the face in front of the ears.
