Capacity should exceed the important data set
Leave room for future files and backup history where supported.
Disconnect or separate when appropriate
A permanently connected drive can be affected by some of the same accidents or failures as the computer.
Label drives clearly
Knowing which device and backup set belong together prevents confusion.
Replace suspect drives
Repeated errors, disconnects or unusual noises deserve caution and professional data-recovery consideration when important files are involved.
General consumer technology information only. Interfaces and menu names change. Before resets, reinstalls, storage changes or other major actions, verify that important data is backed up and use current manufacturer/service-provider instructions.