how to talk to autistic friend

i have a friend who's autistic and i don't always know how to talk to him. i'll call him M because I don't want to write his full name. To be clear, I know that autistic people are just as much a person as anyone else obviously, but I worry I could be doing things better. I have social anxiety and I'm socially awkward too so I'm not good at telling when I'm doing something right or wrong, socially, which is why I'm worried. School is not in session and when it is, it's online, and we're not in the same classes anyway, so all our conversations are through texting. I think M is good at picking up sarcasm and tone in general and I like texting with him but since everything is through texts, I can't know for sure if he responds well or not to how I do things since I don't see him. I know that every person is different but people have similarities too, so I'll appreciate any tips!! And tell me anything you think of, even if you think it's super obvious, like I said earlier I'm bad with social stuff so it might not have occurred to me. Thank you to all who respond!