I'm curious as to the differences in posting style though. What sets the newbies apart from the vets?
It's usually just in the way they ask questions or what they seem to already have a grasp of, for me. When you've been in the game a while, there are just things that you know from being around and hearing the questions asked numerous times, so when someone asks them, it's a pretty good indicator that they're new at the whole thing. Which is exactly what conferences are for! There's also a nervous attitude about newer writers, a kind of "I know this isn't very good but I'd really like your feedback but please don't be too hard on me okay I love you thank you!!!"
Then there are the people who are really newer professional writers but who've been told all their lives that they're REALLY GOOD by people who don't know very much about writing/publishing, and that comes across in their attitude, as well. They're the folks who have to defend every. single. critical. point. other people make about their writing. It's kind of a "yes, but..." or "well you just didn't get what I was trying to do" attitude, rather than saying "thanks for the critique." It's basically their way of saying "my writing is fine and I really just wanted you to tell me it's good." Which is a newbie marker because ALL writers are constantly improving, and denying that means denying that you still have a lot to learn.
There will always be critiques that you aren't going to take, and that's part of being a writer and knowing your own style. The difference between newbies and vets is newbies get really affronted or defensive. Vets just shrug it off and say "thanks."
That's why I tend to frame my critiques with some kind of praise and use language like "my suggestion is..." rather than "you need to do this." It's much easier for someone to swallow when you make it their choice.
RE: Ninja agents. Based on my experience last year, they usually open new sections especially for the conference. They'll post a schedule for when Ninja agents will be prowling the forums, and you can post your work in the special "conference only" forums during those times. They'll definitely explain to you where you should post.