1. don't drink estus in a duel unless it's an invasion or you're outnumbered or the other player has also 2. perform some kind of gesture before you duel to signal you're ready 3. The dark sword and estoc are generally frowned upon because you can easily just hit someone over and over again 4. Don't purposely outnumber a player 5. invasions are rule-free,anything goes 6. In a fight club people will take turns duelling, kind of like a tournament. During one two players will fight while all the others watch, if you try to intervene during a duel you will most likely be attacked by every player there 7. I haven't seen anyone do it but running from a duel likely won't sit well with other player 8. The most used arena is a small area just past the Pontiff Sulyvahn boss in Ithryll