Getting crushed near the rail is the worst thing in the world, as people push you forward, so you push them back... and then the domino effect happens. Person infront of you falls backwards, you fall, everyone else falls.
..and get shoes that fit, normally people will pick up a shoe and hold it in the air if someone loses one but.. some don't.
The gig won't be one huge entire mosh, circles form and you can just stand behind someone on the edge ofi t and they get the brunt of anyone coming at them :P