Initiative Checks: At the start of a battle, each combatant makes an
initiative check. An
initiative check is a Dexterity check. Each character applies his or her Dexterity modifier to the roll. Characters act in order, counting down from highest result to lowest. In every round that follows, the characters act in the same order (unless a character takes an action that results in his or her initiative changing; see
Special Initiative Actions).
If two or more combatants have the same
initiative check result, the combatants who are tied act in order of total initiative modifier (highest first). If there is still a tie, the tied characters should roll again to determine which one of them goes before the other.
Flat-Footed: At the start of a battle, before you have had a chance to act (specifically, before your first regular turn in the initiative order), you are
flat-footed. You can't use your Dexterity bonus to AC (if any) while
flat-footed. Barbarians and rogues have the uncanny
dodge extraordinary ability, which allows them to avoid losing their Dexterity bonus to AC due to being
flat-footed.