Praise the sun. Our Dark Souls Walkthrough provides tips for surviving the adventure, a guide to the entire world, and hints for slaying bosses.
Now that you're armed and ready, it's time to go over the fundamentals of battle. As mentioned previously, each enemy fights differently, meaning that you will have to switch tactics for every new foe in your path.
Be Mindful of Stamina
Stamina governs many important offensive and defensive properties. You need Stamina to run, dodge, block, and even swing weapons. If you run out of Stamina, you might find yourself unable to avoid a painful assault. You recover Stamina faster while standing or moving normally, so put down your shield for when you need a Stamina recharge. This means that you typically can't just roll around or slash endlessly, and will need to pause to restore your lost energy.
Time Your Actions
You can't just swing wildly in Dark Souls. You need to wait and attack when your enemy's defenses are down: mainly while they recover from an attack or block. Some fast weapons, such as daggers, can straight interrupt enemy attacks, while heavy axes might be able to even bash through shields.
Be aware of what stance an enemy is using. Some will attempt to goad you into attacking, only to quickly counter with an absolutely devastating strike. Others will start with a ranged swipe, but might switch to powerful grapples if you get in too close.
This holds true for your own attacks. You can often times use your shield or off-hand weapon to stagger enemies and get in a powerful counterattack. If you're fast enough you can also try rolling behind an enemy and backstab them for extra punishment.
You also need some timing when casting magic and firing arrows. If you are too close, a Soul Arrow might fly over an enemy or you might not have time to cast at all. In general, Miracles force you to sit down and pray (Though some like Force don't require this), so you should cast them while out of combat. If you really need to heal, stick to your Estus Flasks.
When fighting a single enemy you'll want to lock on to make combat easier. However, with multiple targets it's some times better to not use lock-on as this can make it hard to notice your other opponents. You can also lock on and off so that you can shoot guided magic one second, but move around freely the next.
Try to target the most fragile enemy, regardless of how deadly they are. For example, in the Undead Parish you might find yourself fighting several knights at once. Some will be wielding heavy shields and long sword, while others have rapiers and shields. It's actually the heavily armed knights that have less health and should be destroyed first.
Retreat to Favorable Ground
You will often find yourself fighting in environments that put you at a disadvantage. These might include being on a narrow bridge, slowed by water, or surrounded by fire. In these cases, it is in your best interest to lure the enemy into a place where you have the upper hand, or at least an open playing field. It's also good to fight closer to a Bonfire, or simply in a place where you can't be ambushed.
Your weapon of choice might also effect how well you fight in environments. Large sweeping weapons will bounce against walls, leaving you exposed for a few seconds. In these cases you'll want to switch to a spear to thrust forward.
Danger is Everywhere
Dark Souls takes place in a massive open world with very little direction of where to go next. This leads to a lot of exploration and discovery. Be warned, you're lack of familiarity with a new location can be incredibly dangerous. Traps are in places you might least expect, ranging from rolling boulders to fiery blazes. Thankfully, most of these will not reset after resting at a Bonfire. However, enemies will always be lurking around.
Worse yet are assassins and guards that hide behind doors and corners, ready to ambush as you walk passed; often sneaking up out of view of your camera. Move with caution, but be ready to quickly roll or block at anytime. The potential to suddenly be in deadly combat is extremely high.
Death is Inevitable
Face facts: even if you're a high level with great gear and a plethora of knowledge, you will die at some point in Dark Souls. Enemies attack you in droves, often using tricky attacks that can completely breach your defenses. Likewise, other players will often enter your world and attack when you least expect.
This is all part of the experience. Embrace your deaths and use them to ready yourself for the next encounter. Try to recover your Souls and Humanity when you can, but don't get discouraged if hours of hard work suddenly get flushed down the drain. Dark Souls is an abusive relationship. You'll need thick skin and a masochistic heart to love your tormentor.