According to page 7 on PO:C&T, you attack in the direction you are facing:

Normally, characters can only attack enemies in their front spaces and gain attack bonuses when they attack an enemy's flank or rear.

Regarding turning, if it causes you to bring opponents to your rear, they get attacks of opportunity according page 13:

Attacks of opportunity occur when a threatened character or creature ignores the enemy next to it or turns its back on a foe.

I would argue that the reverse is obvious: if you turn to face a creature, you will no longer be able to get bonuses for attacking from flank/rear.

According to page 7 on PO:C&T, you attack in the direction you are facing:

Normally, characters can only attack enemies in their front spaces and gain attack bonuses when they attack an enemy's flank or rear.

Regarding turning, if it causes you to bring opponents to your rear, they get attacks of opportunity according page 13:

Attacks of opportunity occur when a threatened character or creature ignores the enemy next to it or turns its back on a foe.

I would argue that the reverse is obvious: if you turn to face a creature, it will no longer be able to get bonuses for attacking from your flank/rear.