You may choose any of the four core methods you’d like for each of your characters. You don’t need to use the same method for every character.

A character’s original constitution score (after race is applied, but before aging is applied) is the maximum amount of times a character can be raised from the dead or resurrected. Beyond this number, raising is only possible through wishes. Since a character loses 1 CON every time they're raised, without some magical means to recover lost CON it's more likely that the character fails a Resurrection check before they hit their maximum raises.