In a multiplayer game, players may use any mutually agreeable method to determine seating order after they've chosen decks but before the game begins. If players can't agree, they should be seated randomly.

Teyo, Geometric Tactician's last ability doesn't affect creatures that enter the battlefield attacking.

If Teyo, Geometric Tactician's last ability and another similar effect disagree on which direction three or more players may attack, players can't attack at all.

Teyo, Geometric Tactician's last ability affects only what players and planeswalkers each player may attack. It doesn't affect what players may be targeted by spells or abilities or other interactions.