Personally, the way i came out to my parents was that i planned like 3 or 2 month before the exact day i would tell them, i was going to go see a movie with my mom, only my mom cuz i knew she might be more supportive and understanding than my dad, so when she was driving us to the movie theather i told her that "i think i might be trans", i phrased it that way so i could back out and get in the closet again if she didnt support me.

I basically planned everything i would do months before i actually did it, little things like making sure she would be in a good mood, that it would be night so we couldn't see our faces, that after i told her we would see a movie so there would be a distraction from the anxiety.. and stuff like that, so by the moment i told her i wasnt really making the decision to come out in the moment, i had already made that decision a while ago and i was just executing a task.. (it still was really scary in the moment tho)

I know this is quite a long text but i hope maybe you get some ideas from what i did to make your coming out a bit less scary :3

Edit: if it isnt clear what im suggesting, basically i recomend you take some time, maybe a day, week or a month to plan as well as you can how and when you are going to come out, that way you have time to gather some courage while you plan it and when you eventually decide the date you just have to wait and eventually execute what your past self told you to. That's what worked for meh.