There's online resources about the condition and what to expect and how it varies. Brushing up on that can help with interacting with people who do have Autism. However, there is still a componant to it that is out of your control and isnt autism. Some people are just awkward, or use their condition as a reason not to do things that are part of more normal everyday parlance. Things like this can be helped out with them seeking therapy and what not to help address or adapt to those issues. But it relies on them actually wanting to go get help and work on themselves. If they have no desire to do so, there's not much you can do at the end of the day (without completely compromising yourself, but at that point it's not a healthy relation/interaction).

Just brush up on the info, and be open to people. And if people drift and you know you put in effort and tried to be welcoming, well, thats all there is to it. Shrug shoulders and be your own person. If they come to and try, then be open to that. Pretty simple.