When can I declare Power Attack and Fighting Defensively?

[donato]

Simple question. Do I have to declare those as part of an attack or may I declare those at any point in my turn?

For example, if I wish to move and I know it will provoke an AOO, can I declare I will fight defensively this turn to give me a bonus to AC as I move if I still do an attack action?

[Dennis Baker]

"Fighting Defensively as a Standard Action: You can choose to fight defensively when attacking. If you do so, you take a –4 penalty on all attacks in a round to gain a +2 to AC for the same round."

So basically you have to attack first.