I had been on a few forums before I made my way to Elliquiy. So I jumped in with both feet and just started posting in any thread that grabbed my attention at the time. It is not something I would recommend to everyone. I have had good luck with trial and error as a learning method but it can lead to epic failures and much embarrassment.
You could always just read any of the threads that interest you until you get a feel for them. I have found most members to be very friendly. If something catches your eye, you could always send them a private message and ask them about it. You may even make some new friends in the process.