>Is there a way to practice PK without any consequences? A
>'friendly spar' or something similar?

There's an arena near Galadon where you and another character can consentually non-fatally fight.

That being said, keep in mind that what to do once you're fighting, while a very important part of PK knowledge/skill, is only a part. For example, basic area knowledge is crucial in getting to your prey when you're on the attack and avoiding predators when you're not.