It can be very small things. Personally, if games have a character creator, I can't play games as my assigned gender. Impossible. If I chose my assigned gender, I will rather not play the game at all.
In my (transfemme) case it was not tucking an then discovering tucking.
I was always under the impression that it doesn't matter because I'm wearing a skirt that i love and you don't see a bulge with it in any way. But I tried tucking and oh boy! It's not about the visuals but it just felt so much better. Just the feeling of being flat down there was heaven 🤤
For me, it's the clothing I wear. Like when I worked out, I used to wear standard masc workout clothes. But once I discovered sporty fem fits that I look good in, I loathe whenever I have to wear my masc clothing. I like how I look with fem clothing so much more.
I also started growing my hair out and once I saw how I looked with it, I cannot go back to short hair anymore. The simple thought of going back to short hair makes me feel so dysphoric. Plus the compliments I get about my curls which certainly helps.