There is a good (if a little too mathematical) article on how to maximise your Experience points here (http://forum.knightonlineworld.com/viewtopic.php?t=3433&start=0). Priests in particular should note the value of debuffing skills as you can knock off 42% of a monsters defence points before anyone else even attacks! And they can do this from Level 11 upwards!
TL.
I'm not good in math and just got a whole English lesson to study...
Got a shortend version?
Duvel who is to pissed to look at all the English text ;)
In short:
"If it moves, kill it. If it moves toward you, kill it harder. If you can't kill it, hide behind someone else or run away."
Just like cs then :D