Supplement Four said:
For example, you're in a 10' wide hallway. You're fighting an enemy on the left hand side of the corridor. Your ally is behind you, fighting a second enemy along the right side of the wall.
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Your enemy has nish. He swings. You dodge and get the Dance Aside effect, so you move diagonally to the left hand side of the wall.
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Now, it's your turn, and you use your freebie 5 foot step to create a flank on your Ally's enemy.
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This would also work if your ally was in combat way down the hall. Many times, the Dance Aside is a way to disengage from combating a foe without taking an AoO from him.
Take the example above, but change the Ally fighting to 20 feet away. You have Initiative, but you use the Delay option to change your nish to go after your foe. He attacks, and you dodge. You get lucky that he rolls lower than half your Dodge AC. This allows you to Dance Aside, which is to take a free five foot step. It's an Immediate Action, so you do it right then.
Your Dance Aside takes you to the position shown above. Next, it's your turn. You're out of danger now, in no other's threatened area, so you use your Move Action to move 15 feet to your Ally's foe. With your Attack action, you've now made a flank with your enemy, so you get +2 on the attack.
Your ally goes next, and he also gets a +2 attack now because of the flank (unless the enemy used Dance Aside to break the flank from your attack!), kills the baddie.
That would be the end of the round. Now, the two of your turn to face your original enemy, two on one.
Tactics.
I definitely want to encourage this in my game. Certainly, the NPCs will be using these methods against the PCs.