I don't know how many times this idiot got reported on forums and in-game but i hope i am reporting last time. Video shows enough evidence.
Approach a potential opponent and use up/overhead block to request a duel.
Wait for the other person to respond in kind, if they do not, move along.
Do not attack your opponent immediately after a duel request has been accepted, give it a few seconds before initiating the fight so that both players are fully ready.
Do not 'face hug' your opponent before the duel has started.
Be respectful to other players at all times.
Give adequate space to people engaged in a duel, especially if you are preparing to start your own duel.
Dismount your horse in the orchard area (close to the map edge where the horses despawn) or kill your mount if you intend to use a cavalry class for duelling.
Attack anyone other than an opponent that has accepted your duel request.
Interrupt or otherwise disturb an ongoing duel.
Use any form of ranged weapon (bows, crossbows, throwing weapons, etc.).
Duel while mounted.