Several copies, several places
Keep several copies, on different media, including one outside the main server. An incident must not take down production and its backups at the same time.
Restore regularly
A tested restore tells you two valuable things: the backup is usable, and you know how long it takes to get back up and running.
Write the procedure
On the day of the incident, nobody should improvise. The procedure fits on one page. It is part of our cloud & hosting support and of our contracts for keeping the product alive.