I stopped by the Slipknot forums earlier to take a look at what people have been saying about the band's past shows on the tour, etc., before I head out to see them tonight.
On there is a posting all about mosh pits. People are asking what they should eat and drink before heading into a pit. Also, during "Spit It Out," singer Corey Taylor will have the crowd hit the floor before jumping up - if you can "pass the test."
Anyway, it cracks me up about the pit conversations. People are suggesting drinking water, tying double-knots in shoelaces, taking deep breaths, wearing light clothes since it gets hot... The funniest suggestion was "avoid eating any kind of beans" since people are packed in tightly.
Over the years, I've been kicked in the head, punched just about everywhere, kicked in the back, had people land on me, landed on other people and received a variety of bruises of all shapes, sizes and colors. Though sometimes I miss the adrenalin rush, I'm too old for that crap now.
My own suggestion is to not get involved if you don't know what you're doing. Or taking a key from amusement parks "You will get punched on this ride. Arms will be flailing, feet will fly high and you will wake up with bruises having no idea where they came from. Blood is a possibility. Enter at your own risk."
Mosh pits mostly disappeared with grunge (and replaced with pointless jumping up and down), but you still seem them appear from time to time. There's also this crazy shit called "The Wall of Death."
Taken from the scene in Braveheart, a mosh pit will split down the middle and people will run at top speed into each other usually at Lamb of God concerts, but just about every metal group has picked up the cue and gone with it.
In general, here's the best advice don't get hurt.