Hopefully I can add something here. I know I'm new to this site. But I used to help design and maintain parks (Winter Park) and worked very closely with ski patrol (along with doing their end of day sweeps).
If you have friends who are just learning have them watch from the side, DO NOT LET THEM go into the park if they do not have the ability to manuveur around the jumps, rails, etc. Worst injury I've every seen (well aside from someone dieing; was this situation).
If a jump or obstacle is blocked off (board or poles crossing off the front) go around. Don't test the park crews, nothing pisses them off more and they CAN get your passes pulled or do it themselves. You never know why the item is blocked.
If you're gonna duck a rope into the park (which you shouldn't) stop before going under and wait til the it's clear.
If someone is hurt or potentially hurt...GET PATROL. Do not try to tell them they're ok or move them. Getting patrol and guiding the riders above out of the way is the best thing you can do for them.
On jumps with multiple angles do not be afraid to be the one to back off if someone doesn't see you. The jump will still be there on your next run through the park. It's not worth risking the collision.
And as said above always, always take a recon lap. You never know what's changed.