We have a cannon rail (round barrel) at my park and basically go straight at it, it seems really fucking imtimidating and scary at first but once you pick up on it, it's all good. Oh and keep you balance about center.
I occasionally enjoy getting shit on by the passing seagull.
My main advice is whatever way you slide, pick up your front foot when you're getting on the jib. My main fear of up jibs is hitting that ski against the rail and nutting it, and picking that foot up hasn't failed me yet. And don't lean too far back.
If your hitting a cannon then your going to want to be an inch or two above the rail when you get on. To do this then i recommend urbaning on, which is when you jump off of one foot and use that momentum to 90 in mid-air. I jump on from the left side of jumps and push off with my left foot. It's all personal preference when it comes to jumping on. As you get better you'll be able to simply jump with both feet and not push off with one. Hope that helped. Now go out there and stomp it bro.
"Time to nut up or shutup."
"I have always wanted to be somebody, but I should have been more specific."
yeah big up rails can be intimidating. just make sure you bring the right amount of speed in, and pop hard but also make sure you get your 90 done in time or things can get ugly.
if you're scared, the first time you hit it just do what i said but err to whatever side you'd prefer to fall off of, but make sure you get your big pop and 90 on done, and worst case scenario you pop on, slide a couple feet, and immediately jump off to the side, but it will make you realize it's not as bad as you thought as you come into it. just pop hard and get that 90 done and you'll be fine