If the copied creature has {X} in its mana cost, X is 0. This is also true when calculating the mana value of a creature on the battlefield in order to determine whether or not the creature is a legal target for this spell.

If the creature copied by the token had any "when [this creature] enters" abilities, the token also has those abilities, and they'll trigger when it's created. Similarly, any "as [this creature] enters" or "[this creature] enters with" abilities that the token has copied will also work.

The token copies exactly what was printed on the original creature (unless that creature is copying something else or is a token; see below). It doesn't copy whether that creature is tapped or untapped, whether it has any counters on it or any Auras or Equipment attached to it, or any non-copy effects that have changed its types, color, power and toughness, and so on.

If the copied creature is copying something else, then the token enters as whatever that creature copied.

If the copied creature is a token, the new token that's created copies the original characteristics of that token as stated by the effect that created the token.