I mostly just follow a lot of people I find interesting. Which usually means either cool articles on physics and psychology, or more entertainment styled stuff like video games or music. I mostly share though, not post. I'm trying to post a bit more, in hopes of fostering discussion. But I feel that other users probably do it better. What I did when I first joined hubski was just go through the "tags" section, and look at tags that interested me. Then I'd follow users who shared stuff on those tags. From there, I'd just follow anyone that I saw that was interesting. Ideally, I think we'd want to be at a point where you'd follow people whose content you liked. But as it stands, it's mostly just the same few articles shared around the entire site (from my perspective anyway). So just follow some top users, and jump in. Also thenewgreen is a pretty cool person. I wouldn't say a leader though. nowaypablo seems to lead the discussions in what I'm interested in. And overall I'd say mk is the "leader".
Cheers! and uh_oh is right, nobody's competing. Even post in my tag if you want!