For my records, here is an outline of the steps I took to upgrade FreeBSD from 9.1 to 9.2.
# freebsd-update fetch
# freebsd-update install
(and reboot if any changes were made)
Now, fetch the upgrades that are included in the 9.2-RELEASE. The differences in configuration files will need to be merged manually.
# freebsd-update upgrade -r 9.2-RELEASE
# freebsd-update install
Reboot with the new kernel before the non-kernel components receive updates:
# shutdown -r now
After rebooting, install the new user-land components, and upgrade 3rd party packages:
# freebsd-update install
# pkg upgrade
To delete the old (no longer used) system libraries:
# freebsd-update install
Finally, reboot into 9.2-RELEASE
# shutdown -r now