Use the power and toughness of the creature from when it was last on the battlefield to determine the power and toughness of the tokens.

If the copied creature had in its mana cost, X is 0.

If the creature isn't destroyed (perhaps because it has indestructible), its controller doesn't create any tokens. The same is true if the creature is destroyed but instead of going to its owner's graveyard, a replacement effect moves it elsewhere, such as exile.

If the copied creature was copying something else, then the tokens enter the battlefield as whatever that creature copied, with the listed exceptions.

Except for power and toughness, the tokens copy exactly what was printed on the original creature and nothing else (unless that creature was copying something else or it's a token; see below). They don't copy whether that creature was tapped or untapped, whether it had any counters on it or Auras and Equipment attached to it, and so on.

If the copied creature was a token, the new tokens copy the original characteristics of that token as stated by the effect that created the token, with the listed exceptions.

If the original creature had a characteristic-defining ability that determined its power and/or toughness, that ability is not copied.

Any enters-the-battlefield abilities of the copied creature will trigger when the tokens enter the battlefield. Any "as [this creature] enters" or "[this creature] enters with" abilities of the copied creature will also work.