It's very important to know when to strike with Artorias. I've found that keeping your distance and dodging his attacks when he tries to get close is a good way to get hits in while avoiding damage if you don't have a high stability shield. Also, when he tries to charge up, run in, two hand your weapon and start wailing on him. He gets a defence buff when he charges but if you manage to break his poise he won't get his huge attack bonus and will be stunned for a second. That's pretty much essential to know since a buffed NG+ Artorias can easily kill even tank characters in a couple hits.
As for PvP, I'm not really that experienced. I've heard some bad things about the township, but you're pretty much going to find the same shit in every PvP hotspot so I wouldn't judge it based on that.
I have heard that the Moonpit (The moonlight butterfly area) is pretty good but when I went there with my level ~100 character it was a lot less active than the Burg. I've only ever been able to fight 3-5 different people there so I can't really attest to its quality.
Really though, if you want actual quality PvP you should probably join a fightclub with a group of people you trust not to be jerks.