You kill another player.
You then wait by his corpse until he respawns, and then kill him again. You then repeat this over and over again. Please note that this does only work in games where players respawn next to their own corpse. Please also not that players who use this technique is as unwanted as players who camp or Ghost in Counter-Strike
B: k, where are you now?
A: Here around Ironforge
B: Stay there, I'll be there shortly....
*A and 50 others kills B 50 sec. later and then corpsecamp on his dead ass for 5 days