How can I move my installation to a different domain or host?
Backup the existing database and server files. Copy them to the new domain/server and update the library/config.phpfile with the new database details as required. It may be necessary to set permissions for the data and internal_datadirectories to world writeable (CHMOD 0777). Lastly, update the Board URL in the ACP -> Options -> Basic Board Information, if it has changed.
Note that if you are moving to a different type of web server and have Friendly URLs enabled, you will need to make the appropriate changes. Refer to the Friendly URLs section of the XenForo Help Manual for more details.