This "Mosh Pit 101" is in response to Wyldwing's comment about the Demon Hunter and Living Sacrifice concert that I went to a couple weeks ago. Questions or comments are welcome.
How about giving us a "Mosh Pit" 101 class so that those of us who have never experienced one...and never will...can know what it's all about! 
Source: http://www.dragonshobbies.com/comments.php?blogid=747
First of all, I think the best songs for moshing with have quick, choppy rhythms, like what you hear in many of Metallica's most popular songs. (Some songs only have portions good for moshing. If you can headbang too a portion of a song, you can probably mosh to it.)
Now, once you've found a good rhythm for moshing, the next part is to find some people who are interested in joining the fun. Since the center area of the venue is generally the preferred place for moshing, the space may already be open. In this case you'll probably find a mix of people interested in moshing and people who hate moshing. I know, it's strange but the primary reason seems to be that there are people who didn't show up early enough to get right up next to the stage, but they still wanted to get close. This puts them on the outskirts of the moshpit. Some people understand that if they are that close to the area where the moshpit is, they have a chance of getting hit my a mosher who gets pushed/knocked away from the center of the pit. Hopefully this group of moshers is not too hard to find. They are sometimes encouraged by the band playing or by other moshers to get the mosh/circle pit going. Common ways to incite a mosh are by saying "Mosh it up", "Open up", "Get it going", or by moving their hand in the air in a circular motion.
When the group is small, the moshers generally will move around in a circle quickly, as if to round up invisible cattle, until the group gets big enough that people start bumping into each other in the circle. At that point, they break out of the circle and start slamming into each other toward the center of the circle area.
At this recent concert I experienced something that the other guys referred to as "Walls." It was kind of like what you'd see in movies about historical wars where there would be a line of people across the field (or in this case, mosh pit) from another line. At some point, someone would start running and both lines would collide in the center of the pit. Sometimes there were wounded who would fall away instantly, others would keep the action going, slamming into other guys until everyone was too injured or tired to continue.
In two occasions during this concert, a female from the outskirts of that front stage group that I mentioned earlier, jumped into the pit. That broke everything up quickly. As soon as I saw the girl I did my best to avoid colliding with her and immediately broke away from the pit. I ended up next to another guy who said to me, "I can't mosh with a girl." I nodded in agreement. At one other time she got into the pit, after it was already going, and almost instantly the group fell apart again.
Everyone who was fully involved in the pit surely walked away with a bruise or two, if not more. One guy at this show ended up with a bloody lip, I obviously went away with a few bruises myself.
For me, mosh pits are fun and a very important part of the concert going experience. I have been to concerts where there was no mosh pit, or the mosh pit was unaccessible, and those are still entertaining usually, but no where near the fun as getting into the action in the pit.
