In case you were not aware, the recently shipped 10.1.3.4 release of OBIEE includes a sample set of data, metadata, reports & dashboards that represent best practice for OBIEE metadata, report & dashboard development. There are some really good example reports and dashboards as well as solutions to common metadata modeling problems. It's well worth installing.
The sample files are also available stand alone on OTN for those not wishing to download the entire 10.1.3.4 distribution, and yes, they do work with previous 10g releases. Apparently the real trick is actually finding the file on OTN, so to save you the trouble here is a direct link: *LINKS UPDATED*
http://download.oracle.com/technology/products/bi/files/oracle_bi_sample_analysis_setup_files.zip
The documentation of best practices is contained in the following file:
http://download.oracle.com/technology/products/bi/files/oracle_bi_sample_app_content_guide.zip
