Dark Souls is a little different from Demons Souls as far as getting into a game with a friend is concerned. Last time you got the blue eye stone quickly and just placed it and waited to play multiplayer. Here you can miss the stone you need for co op so this guide will help you find it. Let’s go!
Alright in order to do Co op in Dark Souls you will need to do a few things. First off you will need the White Sign Soapstone. This is the item you will place down in order to be summoned. Much like the last game you must be hollowed in order to place the marker and be summoned. Also if you are trying to summon you must of used humanity to turn yourself human again. I will give the location of this stone further down.
The second thing you will need to do in order to play multiplayer in Dark Souls is beat the Taurus Demon. This is the boss of the more upper path from where you came in at. When the raven drops you off go up into the castle a bit and once you clear the fog you will find this boss. We have a guide at https://www.gamersheroes.com/dark-souls-complete-boss-walkthrough-guide if you are having trouble with him. Clear him and keep moving.
Now that he is out of the picture you are almost to Co op in Dark Souls. Keep following the path and clearing any enemies in your way until you make it to a long bridge on your left and a couple sets of stairs on your right. In front of you will be a locked door. Go right and down the steps is a man talking about the sun. Talk to him twice and accept his proposal and you will acquire the white Sign Soapstone. Now you can place it and be ready for multiplayer.
A lot of people seem to be having issues with his at the moment. I am not sure if it is server side or if it really is this hard to join a friend. I did join someone and get summon to summon me a few times so I know it can work. There are tons of people leaving good comments about the situation so check those out and leave one of your own telling us if you got it to work or not!
So far I have confirmed you do not need to be hollow to be summoned. You can be human and be summoned by another human. You cannot summon as a hollow though only be summoned.
That will end the guide now you just have to wait for someone to summon you now! Good luck and happy hunting!