Well I dont know what chat room you are talking about, but unless you change your username, you're pretty much banned until the person with amin powers un bans you. Unless of course they also banned your IP address. If that's the case and you have a dynamic IP address, your pretty much screwed.
As for how to avoid being banned in the first place, if you really dont know the answer to this, you should maybe refrain from visiting rooms in the first place.
Finally, this is a form regarding networking.