I’m still figuring all this out but for me the biggest things were:
Dating app stuff. What to put in your profile, what to talk about when you match with someone, how to convert a match into an actual date
Confidence. After you hit 28 years old and still haven’t been on a single date it starts feeling more and more like there’s something wrong with you. I really had to work hard in therapy to kill that particular demon. The worst part is, you have to kill that demon or nothing will change. You can’t successfully find someone if you believe there is some legitimate problem with you that people won’t accept. And sometimes, there literally is something wrong with you that you need to correct.
Socializing. I’m autistic so a lot of the general rules of conversation, particularly how to have the kind of conversation that makes the other person enjoy talking with you, was really hard for me. I’m still working on this one, but at least for the time being I’ve gotten over the hurdle of getting a steady girlfriend.