I usually leave people alone if I am leveling. If they are killing the same stuff I am for quest then they must die. I dont think its fun to kill some poor bastard who is a lowbie with my 70 and camp him forever. I got better stuff to do with my time. If some high level ganks me I usually kill any red in the area after as payment for the gank. My goal is to reach 70. Once I am 70 I will attack depending on my mood and if I am busy or not. If I am trying to get to an instance for a raid I dont mess with people. I have things to do so attacking would make me late and waste time.
Yesterday I had some jerk 70 kill my 3 51 shamans and the flight guy I was getting ready to talk with in searing gorge. He ended up killing me 2 times each. I was able to finally fly away when I rezed everyone at the fight guy when he respawned. You have to be pretty bored to do that. Once I get my team to 70 I plan on making many alliance pay for my ganks during leveling. And if anyone in my guild is getting ganked I will rush to their aid if I am not in a bg or instance. Thats something The Zerg is not very good at doing so far since I been in the guild. I have been camped by 70's several times while leveling and no Zerg has come to help. Once my team is 70 I will be the one that comes and helps the guys who are leveling up. Maybe when they get camped back they will think twice about messing with a lowbie zergling.