If the copied permanent has {X} in its mana cost, X is 0.

The token copies exactly what was printed on the original permanent (unless that permanent is copying something else or is a token; see below). It doesn't copy whether that permanent 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 permanent is copying something else, then the token enters as whatever that permanent copied.

If the copied permanent 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.

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