(PvE Servers Only)
First off, go to a neutral town, I suggest Gadgetzan.
Now just look for someone of the opposing faction who is not flagged (you must also not be flagged). Once you find someone challenge them to a duel.
Once the duel has begun wait for the enemy to DOT you with anything then enable PvP and do /forfeit.
You should have forfeited the duel and the opposing faction member will now be flagged for attacking you, now just sit back and watch the guards take care of the rest...
Note: Do not attack or place a DOT on you victim as you could then be killed by guards after you forfeit. Also make sure your pet does NOT go to attack your victim after you forefeit.
I searched for similar topic, nothing, but if this is a repost please let me know and provide link, thanks.