It's a fun game, actually, and the rules are very simple:
1) Each post should only be one sentence long. If you absolutely can't get it all into one sentence, then use two, but keep it short.
2) You may post as many times as you like, but you must wait for somebody else to post before you can do so again. (You can't post two times in a row.)
3) Remain on topic. This does not mean that you have to follow a strict storyline of any sort, but keep your contribution at least tangentially relate to the previous few.
4) Try to make it interesting.
The shout penetrated my sleep, but I soon made it part of my dream.