Early on when you are not that strong of a character, the Black Knight in the Undead Burg can easily kill you with three or four strikes. An easy way to defeat him is to stock up on large arrows and throwing knives. You will be making use of the bridge you previously crossed while being targeted by firebombers. Run to the Black Knight and shoot him with an arrow to get his attention. As soon as he starts chasing you, flee back to the room that previously had two axe users and the undead knight. Turn around and close the door. Then, go out on the bridge, take out your bow and arrow, and start shooting him. When you run out of arrows, change to throwing knives. After a few moments the Black Knight will fall and you will gain a nice set of 600 souls. Then, sit at a bonfire and repeat the entire process.