Just go with the standard freecycle rules... they're decent. If you see too many of those postings on your own list, send a friendly reminder fairly often about how a post should be formatted. People usually comply. If a person regularly does not comply then contact them privately. Honestly, the list will mostly run itself, and will probably pick up at least one "freecycle cop" that points out every violation as if you didn't see it yourself.
I have a couple of ways that I differ from the standard Freecycle rules, but the only major one that pops into my head at the moment is that my list is moderated. Being around my email inbox from 8-5 m-f and not that far from it most weekends and nights makes it pretty easy. Yahoo emails you an email for each entry, you eyeball it quickly, hit reply and send without editing. Or you can approve stuff from the website. Either way, I find moderating to be little trouble and lets even less crap through to the list. The reason they usually say "no moderation except on new members" is because people sometimes do that to get first crack at the stuff, and some have even takena a large % to sell on ebay or something. I have taken so few items from my own list that it's not an issue here and I am still the person on my list that offers the most items.
The setup and approval process is a PITA, but once you're up and running, there is actually very little to do other than the occasional member question, especially if you don't moderate the whole membership.
People really seem to like the concept and whenever I meet one of my members they always thank me and tell me how much they appreciate the effort. I use the list a lot myself but only sign as Owner or Moderator when actually acting in that role. If I'm offering or asking for an item I just sign with my name.