Back up before you touch a server. Every time.

My rule is simple: before any deploy, upgrade, config change or even "just a quick look" at a server, I take a database dump first. Not because I expect things to break, but because the one time they do, the dump is the only thing that matters.

The routine is short: dump with a single transaction, gzip it into a timestamped file, test the archive, and write down the row counts per table. When the work is done I count again and compare. If the numbers match, I know I didn't touch the data.

Nightly backups on the same machine are not a backup strategy. They protect you from a bad query, not from losing the server. Keep one copy somewhere else, and test a restore at least once. A backup you've never restored is a hope, not a backup.