This is one of my favorite Joseph Lstiburek articles
http://www.buildingscience.com/documents/insights/bsi-015-top-ten-dumb-things-to-do-in-the-south/?searchterm=roof%20design (http://www.buildingscience.com/documents/insights/bsi-015-top-ten-dumb-things-to-do-in-the-south/?searchterm=roof%20design)
#1 is my favorite "not to do"