hi! that's a good question! i'd say that the main things to keep in mind when talking on forums is that, unlike social media, this baby is largely collaborative! when you post a new topic, it's because you want to talk with a bunch of people on a specific subject. so take an interest in other people's thoughts! ask about their opinions! ask to see their art! reach out, and everything should go perfectly.
oh, also, posting is slower, so responses will be longer. feel free to get kinda dramatic with it. i like to imagine i'm writing letters to a long lost friend, off in The War.
you're doing good so far!