My experience is that cliques are a human behavior, not an AA behavior. I've experienced them pretty much everywhere there is a large group of people involved. I refuse to behave that way OR let their behavior bother me (anymore). I will admit that cliquey behavior in AA (and at work) used to bother me a lot until I came to the realization that I'm not there to make friends, I'm there to save my ass (or in the case of work provide for myself). That doesn't mean I don't make friends, only that it's not my primary purpose.
I would say the single thing that helped me the most was finding a sponsor and working the steps. It gave me a whole new attitude about life, myself and others. Another thing that helped was getting involved with AA through commitments without expecting anything in return. It was amazing how much something as simple as helping to set up meetings or cleaning up afterwards made me feel like part of the group.