Fic exchange will probably happen more around Hanukwanzmas/other holidays I don't know about, or celebration times like beginning of summer and stuff. (Note, Worldly people, are your summer months the same? June, July, August)
Generally I've seen it run like so:
Sign up: this entails committing to writing fic/drawing art/movie/any creation form, and maybe giving a prompt for the fic/art that you will receive.
The mod(s) (currently just me) will pick names and prompts out of a hat and assign them to people.
Then period for creating.
Then either people email the creation to the mod (I'll be using illusionprompt@gmail.com for exchanges as well) OR they will just post it as a thread on the forum with a heading like "Title" fic/art/movie/other creation for so-and-so.
Then there will be rejoicing over the creations! It's all very exciting.
The emailing thing is if I decide for the contest to be semi-anonymous. That way there isn't as much pressure on making something ABSOLUTELY AMAZING AWESOME /capslock and is more fun for the participants.