Well, the way my people joined our team:
Koronis: I got to know him on a private WoW server's forum. I did a lot of coding for his map, and we became friends through the development and testing process. He has things I'm lacking: WarCraft lore knowledge and good imagination. Plus, my English sucked far more back then. Every project I started afterwards was with him, including IID.
Hellx: I was using a few of his icons, and when he posted a new one, I noticed that he was from Hungary, like me and Koronis. I started a conversation with him, but we were just talking, really. IID was in a desperate need of a terrain rework, and he said he could do it. He showed me a few pictures of his previous works - I didn't like the tileset, but it showed that he has imagination and experience. But I was totally shocked when I saw one of the first WIP's.
Champara_Bros: Drunken_Jackal suggested him, yup, I PM'd him and offered him the Main 3D Artist role in the team. He gladly accepted, and we've been on good terms since then.
Fjury: He found the thread in the MD section, and offered help. He showed me a few of his works, I liked them, so the Main 2D Artist role was his. It's unfortunate that he's been missing for almost a year by now, I really miss him and his work.
Judash: I PM'd her as well - she said she'd make models, but she only accepts complex ones.
So as you can see, I did PM some people, others I either knew before IID, or they offered their help.