Data and backups before the day you wish you had them
Customer lists, photos, contracts, accounting data. Lose them once and you'll never skip a backup again.
Cloud-based primary systems
Customer data, accounting, scheduling in cloud-hosted tools by default. Local-only databases are one hard drive away from a disaster.
Off-site backup for everything else
Photos of jobs, signed contracts, key documents. A simple cloud backup ($10 to $20 a month) covers it. Lots of shops still keep everything on one laptop.
Test restore once a year
A backup you've never tested isn't a backup. Annually, pull a file from the backup and verify it opens. Most shops discover problems only in real emergencies.
Take your version of this question further
This is one operator-tested angle on the question. Your shop, your size, your trade, and your team change the answer. Ask your specific version inside Ask a Shop Owner to get a response grounded in how owners like you actually handled it.