Are there any best practices that need to be followed or are recommended specific to Dimensional reporting.
A good place to start is by taking a look at the Proven Practice documents on the IBM website. You can find the ones related to dimensional reporting here:
http://www.ibm.com/developerworks/views/data/libraryview.jsp?sort_by=Title&sort_order=1&show_abstract=true&show_all=false&search_flag=true&product_by=Cognos&topic_by=All%20Topics&type_by=All%20Types&search_by=cognosppreportingdimensionalqueries&Submit.x=0&Submit.y=0
You might also find it worthwhile to attend one of IBM's dimensional report authoring courses - if memory serves it's two days covering using Report Studio to build reports off dimensional sources.
Regards,
MF.