The active player has priority and all effects must resolve fully before another effect can be triggered, when priority is passed to the inactive player they may use 1 effect and pass priority back to the active player. Remembering this rule solves most timing issues. In the event of a truly simultaneous effect (such as one triggered by dealing damage and one triggered by receiving damage happening when combat damage is assigned) the active player gets to resolve their effects first. Simultaneous effects controlled by one player are resolved in the order of that player’s choice.