Basic backup strategy:
1. Local, hourly, incremental backups. Time machine on an internal or NAS drive is great for this.
2. Bootable clone, updated nightly. I use SuperDuper. This way if something goes wrong you lose almost no working time; you can be up and running in a minute.
3. Offsite physical clone, updated weekly. I store an external hard drive in a completely different building and bring it in once a week to backup everything. Then I move it offsite again. This way, if your apartment/house/whatever goes down in a fire, you still have something to fall back on; you haven't lost your life's worth of data.
4. Cloud-based storage. My email is based on GMail; my current documents all live in DropBox; my contacts etc. are stored in iCloud. Each of these things functions like a pseudo-backup, so if I do lose my local data, there's at least a good chance I'll still be able to access my key files from my phone or a loaner computer.
Remember people, data doesn't really exist until it's in at least two places, preferably three or four.
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