This is much easier if you are a +3 Darkwraith, drain 10 humanity per grab. I've done this a few times, and I also like to kick them around the level a bit, then kill them in a very weird out of the way spot, so they have no idea where there bloodstain is when they respawn.
On a different note, I have been partaking in some awesome Dark Souls PvP shenanigans with people on Twitch.tv. The best game mode that one of the Broadcasters came up with is Guerilla Warfare, it's essentially 2v2 hide and seek/kill. The only rules are no Divine Blessings, and no Elizabeth Mushrooms, everything else is fine, TWoP, Hornet Ring, Healing with Estus/Humanity/Spells, WoG spam, Dark Bead, you name it, it's allowed. It makes it more chaotic and random if everything but the cheapest healing items is allowed, and battles last longer with players healing at will. The broadcaster has a few highlights up on youtube. One of them with Gravelorded Royal Wood as an Arena, and then probably the best spot for good matches, The Depths, where I pull off a ridiculous comeback at the end.
Gravelord Royal Wood
http://www.youtube.com/watch?v=WlE4bTbzXZk
The Depths, with insane comeback by yours truly.
http://www.youtube.com/watch?v=aGehNkiVcHg