Table.find(@params["tag"])

Table.find(:all, :conditions => ["other_column = ?", params[:tag]) #
or :first, instead of :all

Don't use @params anymore, BTW. And although it's allowed, I think
the symbol as a key to the params hash (params[:tag]) is generally
favored over using a string (params["tag"]).

You're welcome. I just noticed I'm missing a "]" in my original post,
by the way.

Table.find(:all, :conditions =>
                   ["other_column = ?", params[:tag]]
              )