1) RESPECT. Treat everyone with respect and common courteousy and they'll do the same for you. (This also covers respecting their decisions for their characters, so don't just go in and kill/impregnate/etc. their character if you haven't discussed it in advance!)
2) DUPLICATE CHARACTERS. These are allowed, as long as the mun of the original(s) are okay with it. Please post a request in the community (or ask over aim if you know) and if you have no complaints within 72 hours, feel free!
3) ORIGINAL/PAN-FANDOM CHARACTERS. We do allows these HOWEVER you must have 2 Tolkien canon characters for each one of these you might have AND you have to clear it with a modly type first. (Odds are we'll say yes.)
4) KEEP IT PG-13. Respect that not everyone may be as comfortable with the sex or violence as you. If you want to play out something like that privately, feel free, but cut it short for things you share. An lj-cut and a warning is STRONGLY recommended if you post anything that might make someone else uncomfortable.