I usually show up about an hour before the gates open. FLWWEFan is right, the lines get quite long. I also try to get there early so I can buy any merchandise right away. As for the camera, I've read before that you can have a camera (point and shoot) and that it can not have a detachable lens (DSLR). They obviously don't allow camcorders, but most cameras/phones do video. I think I remember that they will tell you to stop recording if they see you doing it.
As for other things to expect. It will be LOUD, which is great in my eyes. Sets the mood. There are more pauses than you might think between matches. Try to participate in all the cheering, no one likes a dead crowd. I personally love the dark matches myself. Usually you get to see a local guy (Joe Hennig for me) and the wrestlers will break character more. They won't necessarily follow there heel/face roles and they are free to joke around. That's my experience anyway.
Have fun. Soak in the atmosphere. Be sure to watch the replay on tv or online. You might just see yourself. (Sidenote - I was at the Raw 9/29/08 where Shawn Michaels needed a partner to face Chris Jericho and Lance Cade and Triple H was his partner reuniting DX and I could see myself. It's a great way to show friends you were there.) You'll never know what's going to happen.