Blizzard have detailed how the duelling will work in the upcoming Diablo III 1.0.7 patch as well as class updates, crafting additions, monster power changes, monster affix changes and quality of life improvements.
When wanting to duel, players and their parties will be teleported to a new custom-built PVP zone called Scorched Chapel after talking to a new NPC at the Inn in New Tristram by the name of Nek the Brawler. Up to four players can free-for-all battle in the four areas that make up Scorched Chappel; a church, a graveyard, a river and a lake.
No score is kept and no objectives are on offer, it's straight up no-holds-barred, beat-em-up brawling. Courtesy of Games.On.Net.
Further details of the patch which will be available very soon can be found here.