I came out to one of my friends whom I had thought was very open-minded, at the time I was actually questioning whether I was trans or whether I was just crazy and/or going through a "phase" of wanting to be more masculine. So it was more of, telling her that I was confused about my gender, than actually saying "yeah I'm a transman" flat-out. She didn't react well, and we haven't spoken since.
The next friend I came out to, about a year afterwards when I'd figured out it was definitely not a phase nor insanity

I kinda hinted at it over a few days of texting her, I hadn't made up my mind whether to tell her or not. We were talking about dating (not each other) and I was like "Yeah, I don't really want to date anyone for a while, I'm not really comfortable with the way my body is." She probably assumed I meant I wanted to lose some weight before dating (I had about 20-25 lbs to lose at the time), and I did but that wasn't what I was referring to. Then later on we were hanging out, and the dating subject came up again and she asked me what I meant (I think she was about to say "Well you're not
that fat" or some such thing) and I said something like, "Well... I don't know how to say this, so I'll just say it.... I'm a female-to-male transman." I expected her to be at least somewhat shocked, but she didn't seem surprised at all. So far she's been the most supportive of all my friends.
Everyone else, I just randomly told them. It was all along the lines of, "You know, there's something about me I think you should know.." then I just said, "I'm trans. Don't hate me!" It was basically a 50% success rate, so it sort of worked...

Overall, my guy friends have been much more accepting than my female friends.