really don't need to stir other than if you want to stir the hot break back down on a close-to-the-top boil. The boil itself will circulate the wort. Stirring afterwards while chilling is a definite must if you use an IC.
All that you want. It's most important to stir a lot when the extract is being dissolved. Once it's dissolved, and the hot break occurs, turn down the burner to create a nice small roll in the boil, and to keep the bottom from scalding. Then I stir very little, like about once every 10-30 minutes.
If you use irish moss or whirlfloc, you want to stir to create a whirlpool and then wait for it to settle before racking into the fermenter, as this will land your sediment in a pile in the middle.
At the end of the boil and once the wort cools below about 190F, stirring should be done very gently to avoid splashing. The wort is vulnerable to oxidation of the wort at this point down to around 80F. So be very careful then.