ReleaseEngineering/How To/Send a Machine For Repair
Machines slated for repair should first be cleaned of secret information - see How To/Clean A Slave For Shipment Externally (auth required).
Disable any undesirable startup behaviors - even if you expect the drive to be replaced, the machine may end up back on the network with its existing drive image. For slaves, this means disabling the slave in slavealloc. For masters, it means disabling the service.
Once everything is ready, shut the host down - Ops is much more confident un-racking a host that doesn't have spinning fans. Provide Ops with a clear description of the host - hostname and asset tag, if possible - for un-racking and preparation for shipping.