1) Backup the database BEFORE updating the codebase.

2) Shutdown the server and upgrade the codebase.

3) Start the server and restore the database.

4) Shutdown the server.

5) Start the server manually via

./openerp-server --update=all -d name_of_database --addons-path=/path_to_addons,/path_to_web_addons

6) Watch the console log messages, warnings and errors related to the upgrade process.

7) If all is well, shutdown the server and restart normally.

Ideally, you would do this on a test server - so that when you upgrade your production server you can just backup and restore your upgraded databases from the test server to your production server.