Try the following:
[*]Type /names #channel and check the status window for names beginning with @.
[*]Ask someone else who you know uses the channel (see above).
[*]Type /topic #channel and check the status window for the name of who set the topic (normally only ops can set the topic).
[*]Check the channel's website if it has one (if you don't know the url, see if there is one in the topic (see above)).
[*]Check your logs if you have logging enabled.
There are also many other ways, such as typing /mode #channel +b and checking in the status window if anyone has set any bans, since only ops can set bans.