My first pointer would be to go find some
Groups you like, but I see you've already done that! Good start
My second would be to interact with a few people, comment on their work/journals, give out Llama badges (they don't really serve a purpose other than being a digital badge to collect).
Another thing you can do is to post art and submit that art to groups, if you're an artist, or just post a journal or status update! Maybe introduce yourself. You may not get a lot of feedback at first, but it's good to do stuff in a community!
DeviantArt also has a
Forum and a
Chatroom section, though those are kind of a culture of their own, and many people I know never actually use those sections of DeviantArt, while others nearly only use those parts. So that's possible, too!