I recommend that you follow the recommendations in the
NARAS (Grammy org) Producer's and Engineer's Wing Recommendations for Surround Sound Production document. A lot of thought and work went into making this a very useful guide for setting up surround systems in an effort to standardize systems and techniques as much as possible. Some of the information is slightly outdated, but still very informative and accurate overall.
http://www2.grammy.com/pdfs/recordin...rs/5_1_rec.pdf