Get yourself to roughly 56 poise, equip your best weapon, then just run up to them and hug them while you hit them. They'll maybe hit you with the hilt bit of the weapon, but it won't do much damage at all. usually you can take them down really quickly like this.
Just be careful that they don't grab you or do the exploding move. Them grabbing you can be fixed just by healing, but the explosion can one shot you if you're not careful.
Also, fire weapons are good. If you have those to a decent level (Quelaag's Furysword is great, for example), then use those. Not essential, though.