It’s literally as simple as looking at someone’s chest for some people. It’s called a pronoun pin. ITS NOT THAT FRIKKIN HARD! There’s literally only one person I struggled with, because I knew them for multiple years before they came out. They were attractive, and I had a crush. I pounded it into my head every time I forgot, and it made it a little harder for some other people’s pronouns, but I get them right. If you have trouble with pronouns like this, just use names. And I highly stress only using names for a week or two after they come out, to let your thoughts get into the habit. If you think wrong, no problem, if you speak wrong, someone hears it. I tried to say hell yeah earlier, and didn’t stop myself fast enough to avoid swearing. I don’t swear much, but I swear in my thoughts CONSTANTLY. Because of the link between thoughts and words, just practicing thinking their pronouns correctly will get you into the habit.