pits are when a group of headbangers
or anything like that start to fight amongst them selfs.
This usaly includes:
Throwing your arms around to protect your own personal space.
Teaming up with a friend and spinning around so that you can both go flying into the crowd that soon gathers around.
Frantic pushing and shoving to get into the middle of the pit and join in with the singing(but more likly screaming) of the lyrics.
I have encountered three forms of mosh pits, grudge pits(where you pick a foe and dont stop fighting with them untill the music carms down), Open pits(where you can actually move and possibly hit other people), and closed pits(in these you can move very little)
go to any venue where rock music is being played and ask for any slipknot/killswitch music...or even lost prophets fake sound of progress