I am of the school of thought that figures the only reason for quoting previous content is to provide context so the new message will make sense. Following this reasoning, the context should be established first. HOWEVER, it is very important to trim the quote so that it only provides enough context and doesn't go overboard and turn into spam. Ever seen the TV program "The West Wing"? They start most programs with a short "previously on The West Wing..."-bit. It comes first (so the following program will make sense) and it is shorter than the new program (even though it covers more territory--the idea is that it be the new stuff that is important).