Praise the sun. Our Dark Souls Walkthrough provides tips for surviving the adventure, a guide to the entire world, and hints for slaying bosses.
Online Multiplayer
You might be alone in Lordran, but parallel worlds are all around you. As long as you sign into PSN or Xbox Live you will be automatically taken into Online mode. If you wish to play on your own, disable your internet connection.
There are several activates you may engage in with other souls: giving helpful hints, joining forces, or attacking other players.
Other Souls
As you roam around the world you may spot other players in Soul form as they attempt to complete their own quest. In some cases they may leave behind their own blood stains. If you click on a fallen player's blood stain, you can witness the last few moments leading to their demise.
Messages
In the Undead Burg you can purchase various items from a merchant. Among them is an Orange Soapstone that will allow you to leave messages for other players. Even though you can buy multiple Soapstones, the item is not consumed when used.
You cannot fully customize your messages. Instead, you enter a number of statements from a list of dialogue choices. For example, you might leave a message of "Be wary of Right" to let people know that there is an enemy hiding behind the corner.
You can also use messages to outright lie, giving other adventures a false sense of security when trouble is abound. However, messages can be rated by other players. Messages that have high scores may reward the writer with bonuses or an instant heal. It's your choice if you want to aid or hinder other users.
Cooperation
After defeating the Taurus Demon in Undead Burg you can encounter a white knight of the sun. He will offer you a White Soapstone that can be used to join with other players. To join other people's worlds place your White Soapstone down on the ground. You may do this in both Human and Hollow forms. As long as you stay within a minimum range and not near a Bonfire, you can be summoned by other players.
To invite other players you must be a Human. Locate the other player's Soapstones and summon them into your world. As the host you can invite two others to join your team. While working together you can defeat bosses and other enemies as a team. This can aid the Human to complete areas that were far too challenging. Guests are rewarded with bonus Souls and Humanity for aiding the host player.
A warning though: if the Human host should die they will become Hollow and all guests will be banished from his world.
Invasion
Eventually you can find Cracked Red Eye Orbs. These can be used to invade other worlds and engage in player vs player combat. Killing other adventures will allow you to steal Souls and Humanity, and also cripple their progress. Red Eye Orbs are consumed even when you cannot find a victim for invasion.
Your main goal as an invader is to kill the host, though disposing of any allied guests will make this process much easier. In general you should remain hidden and ambush when the host least expects you. In other cases you should attack while the host is already engaged with a strong enemy. This will leave them distracted and unable to defend themselves.
The host and his guests are most likely headed for a boss room, so you may want to head there if you spawn in a strange location. However, the host can chicken out of a fight by reaching the white light of a boss door and entering inside.
Be warned though, killing other players can lead to the wraith of the Darkmoon. Your victims can purchase Books of the Guilty from the Undead Parish and take revenge on you by adding you a hit list. By being on this list you may be constantly attacked by powerful black knight minibosses.
No Direct Communication
Dark Souls is a lonely experience. Even with other players on your side or after your head, you cannot use built in voice chat. This means there is no forming a plan with your team or taunting your victims.
Instead, you will have access to gestures that will help get your point across. These start out as pointing in a direction or sulking in defeat. As you talk to various NPCs they may teach you more gestures to help interact with other players.
If you have a motion device--such as the PlayStation 3 Sixaxis--you can perform gestures without entering the menu. Simply hold your confirm button and flick your controller to make a gesture.
Covenants
Covenants are organizations throughout the world. Being a member of a Covenant has benefits both within singleplayer and multiplayer. There are nine Covenants total, each which have their own strengths. You should pick one wisely, as breaking their rules can cost you dearly.
One example of changes to multiplayer is from the Way of White. All members of this Covenant will be able to join each other easier and will be given benefits from Miracles cast around them. They are also better protected from enemy Covenants.
Some Covenants are designed to harm other players. Members of the Forest Hunter gain bonus Souls and are summoned to kill other players within the dark forests. Gravelord Servants can force extra enemies into other player's world and steal Souls, but can be easily invaded themselves.
Other Covenants don't have direct effects on multiplayer, instead granting access to new spells, extra healing items, or making allies out of enemies. Pick the one that best suits your play style and be careful to not betray their trust.
If you do break a covenant (or simply want to quit one), head to the top of the Undead Parish bell tower and speak to the black garbed NPC there. With his aid you can abandon a covenant for free, but it will cost many thousands of Souls to remove any sins commited.
