I've havent played on PVP servers much, so this has to be taken with a grain of salt :)
PVP tacticts I guess would relate very much to your class selection and to a lesser extent the opponent.
A couple of ideas:
The bard is repulted to be a godly PVP class, I think - plus very hard to kill cause they are so hard to catch !
Wizards, when they have made it thru the lower levels, should be able to cause a frey. Sit in wait, invis if you please, target and move out of sight. BAMM !! BAMM !!