locking on doesnt seem to do anything.

[static addict]

what is the trick?

[ProgViking]

It's not very apparent but your camera will follow NPCs if you press lock-on.

["MrHindsight"]

I thought so too at first. Turn it on with F if not already (the circle will implode on itself) and swing your weapon as far as you can left/right. Notice your camera direction. Then, turn it off (white circle emanates from the center instead) and do the same with your weapon. If you'll notice the camera itself* will no longer lock on to the enemy, and instead moves away from the target.
I hope that helps!