To start a duel you:
1. Make steady eye contact and point to clearly indicate the individual you wish to duel
2. Quickly close the distance between you and the individual at a swift walking gait.
3. Loudly declare your official request to initiate the duel

Coincidentally, when interacting with territorial pokemon, the most important steps are
1. Avoid Eye Contact with the Pokemon or any members of it's pack
2. Slowly back away from the Pokemon and keep your body language subdued
3. Do not make any loud noises as this may startle the Pokemon.

For some reason there has been a surge in hospitalizations due to Pokémon attacks.