1. Block is Your Friend
Blocking is absolutely essential in Dark Souls. I've found one of the most useful skills for survival is to constantly block whenever you're moving, ensuring that if an enemy attacks from the side or suddenly from above or something to that effect, you're protected from harm. If you hold down the block button, your character will constantly have his/her shield ready and will more than likely deflect an enemies' first blow, giving you ample time to get in a few cheeky hits. When in direct combat, block your enemies' strikes carefully, wait for an opening and strike only when you feel confident the enemy won't react suddenly and hurt you greatly. An integral part of learning to block effectively is also getting a good shield; larger 'tower' style shields are much better for blocking, and will deflect most enemy blows without any damage to your health. Smaller shields with lower resistance run a risk of still inflicting damage even if you block, so I'd recommend using the larger. Don't bother with learning to do the parry attack; this is an extremely advanced skill and will leave you completely open to attack if you mistime it. Learning to block effectively will serve you much better.