WOW PowerLeveling: The single biggest difference between PvE and PvP is positioning matters
Play to win: Don't pick skills or use WOW PowerLeveling tactics based on the assumption that your opponents will be bad. They may well be but then you'll win anyway. Worry about the cases where you'll face someone who knows what they're doing.
Game-play: Location, location, location
The single biggest difference between PvE and PvP is probably that positioning matters. You can get through the whole PvE game and never move when monsters are beating on you. This is not the case in PvP.
If there's a warrior about to hit you, you probably want to run away. If they're already hitting you and you weren't casting anything a second ago, you already made a mistake.
If there's a ranger shooting you, put a wall between you and them. If an Element list is zapping you, they can't do it if you're out of range. In short, watch the battlefield. If someone's running up to you it's probably not to give you a hug.
If you run out of healing range of your monk, they won't be able to save you if you're in trouble. Be aware of where your monk is. You can use this against your opponents too - if you can draw an opponent away from his group they may well be easy pickings.
