Anor Londo Coop?

I don't go human all that much, so I'm not too familiar with coop, but I was looking for some help with S&O. Is there some etiquette I'm not following correctly or what? I've summoned people a few times, and been invaded a few times, never attacked, so I assume the guy was going to help me out. Basically they end up following me to the white door and then when I go in, I get the "xxx has returned home" message. I've run past the big knights and waited at the door as long as I could, I've killed both knights and the archer and then went and stood by the door. I got sick of being left in the lurch, so I've summoned Solaire, but then he attacks the player, who then kills Solaire, and leaves me alone for S&O.

What exactly am I doing wrong?

You sure you're not summoning a Dragon or someone through a Red Soapstone?

If you summon a player via Red Summon Sign, or via Dragon Eye sign they're there to fight you, duel you, not to help you. Same to players that invade you, those are there to mercilessly slaughter you.

Of course, you may bump into a friendly player that will gladly help you, but they can't fight the boss with you and the game will send them home as soon as you enter boss's room.

Solaire is an AI, he doesn't understand human thinking, he just sees a potential enemy and attacks.

Summon players only with white and gold signs (just like Solaire's), those are there to help others and with them, you can challenge the boss. You can find those in different areas, usually close to bonfires, or boss fog gates.

When you summon them, remember that you can use your Estus Flask to heal your phantoms. They can't use their own Estus Flasks and while they can use Healing Miracles and Humanity items to heal, they take time to use and so will rely on you to heal them, while they fight for your sake.

If you're on PS3, I could help you as much as you'll want. I'm usually online at 14:00-18:00 EST / 19:00-23:00 GMT(UTC).

EDIT:
If you're on Xbox, or PC, try looking, or asking for help in this thread.
Co-op services thread.
Our members focus on helping others.

I've only summoned from the white/gold summon signs, and been invaded, but the invaders didn't attack me for some reason. So I guess they were friendly - I wasn't aware that invaders couldn't do the boss fight. I guess that makes sense though. That's why those guys dropped off when I went thru the fog. I'm not sure why the summoned guys dropped off, but maybe I'm thinking of the time I ran past the Knights and maybe they got killed behind me? I'll have to try it again.

If I summon somebody from a white summon sign, and I go thru the fog gate, does it matter where the summonee is at the time, or do they automatically show up at the boss fight? Do I need to wait by the gate for them to be relatively close or something?

I'm on PC, but thanks

Summoned players must go through the fog themselves, so if you rush to the boss, they won't teleport there. They have to go there same as you and if you rush through the area, you'll aggro enemies on you and those enemies will attack your phantoms and they might've died to them, or got stuck fighting them.