In this section

Historical Rules · 1 October 2012

Rule 808.4

Official source text from the 1 October 2012 Rules release

To determine which player goes first, randomly choose a team. If that team has an odd number of players, the player in its center seat goes first. If that team has an even number of players, the player to the left of its midpoint goes first. Turn order goes to the players' left.

Find this number in the current Rules