I apologize if this is posted elsewhere but below is a process I followed that worked in performing an upgrade plus left me with backed up versions of the old DB and files. I hope someone finds this helpful.
# DB backup and new DB creation
* create sql backup of your “old” magento DB using phpmyadmin or similar
* create new DB on your server
* using phpmyadmin or similar import the previous DB content (sql) into your “new” DB
* edit local.xml to point to the “new” DB
# download “new version” of magento
* unpack new version of magento on “local machine”
# copy /app/frontend/"theme" and /skin/frontend/"theme" directories from your website to the new version of magento on your “local machine”
* copy /app/etc/local.xml from your server to your “local machine” (similar to the above step)
* copy local.xml to the /app/etc/ directory of the “new version” of magento on your “local machine”
# upload the new version of magento (with your merged critical files from above) to your webserver (if the FTP gods will allow, this will occur on the first attempt--- although it never does for me)
# once the “new version” of magento is uploaded on your web host, rename your old magento site (to save it for possible restore/ backup)
# rename the “new version” of magento to represent your website naming convention = to the old site name
# run the site and everything should work! PLUS you will have a new clean DB and a backup of the old version of your site! Such a deal!