The best backup you can have is a BOOTABLE cloned backup created with either CarbonCopyCloner or SuperDuper.
Get an external drive that is equal in size (or larger than) your internal drive.
Then run either of the above on it, and update your backup at regular intervals.
With a backup that's fully bootable, if you ever experience an "I can't boot!" moment, all you'll need to do is connect your backup and chances are you'll be back up and running in a couple of minutes, and can work on the problem from there...
You CAN'T do this with a Time Machine backup.