Posted this in the main thread too, but it clearly moves way too fast:
Found some info on reddit that could help folks play co-op with friends
HOW TO EASILY CO-OP WITH FRIENDS
I'm not sure if many have figured this out yet, but I haven't really seen it posted here.
I was watching a stream of some dude playing Dark Souls the other day and he was constantly summoning his friend into his boss fights/areas. I asked him how he did it and he happily told me. Apparently, whenever you drop your White Soapstone, it's placed on a random server. If you drop it again, it's placed on a server different than the one it was before. So a buddy of mine thought we'd try out this guy's method of summoning his friend. My friend would drop his soapstone, and wait about 20 second, and drop it again until I told him I seen it, which I did eventually, every time. Sometimes it took five minutes, one time it took around 11 minutes, but that's because the first two times I seen his stone, he dropped another one before I told him I seen it, so the summon would fail.
TL;DR: Drop Soapstone near buddy every 20-30 seconds. Buddy should see it eventually when it lands on his server. Summon him up