The guidelines below can be followed when testing new releases:
Read the Release Notes to familiarize yourself with improvements/fixes included in the software. This should include not only the Release Notes for the version you are installing, but also any Release Notes for versions you are skipping over during the upgrade. For example, an organization upgrading from version 7.10 to 7.12.4 should read over all of the Release Notes for versions 7.10.1, 7.10.2, 7.12, 7.12.1, 7.12.2. 7.12.3, and 7.12.4.
Click around to various Pages and verify that they render as expected.
Publish a number of Pages to a staging/test server and verify that they are transmitted to the web server(s) as expected.
Verify that existing Web Services scripts run as expected. The Web Services Change Log should be used to identify any updates that need to be applied to existing scripts.
Verify that any custom plugins (Asset Factory Plugins, Publish Triggers) work as expected. Plugins that require recompilation will be mentioned in the Release Notes.
Send a handful of assets into commonly used Workflows and verify that they complete without errors.
If using LDAP for authentication, run a test sync and verify that LDAP users can log into the application successfully.
If using custom authentication (Shibboleth, CAS, etc.), verify that custom users can log into the application via your authentication portal.