Most of us already know that we should back up our work. What I'm going to strongly suggest with this post is using multiple forms of backups as opposed to just one.
Recently, I was in the middle of renaming a few of my manuscript files when a few of them became corrupted. Some of the files refused to open at all and the ones that did open were still unreadable. The glitch ate most of my work.
The cloud service that I use to automatically sync my work to my other computer as a back up proceeded to sync those corrupted files to my other computer before I could retrieved the undamaged versions of those files.
Fortunately, the day before this incident, my work had automatically backed up onto an external hard drive via Time Machine. If not for that back up, I would have lost my entire manuscript! But I was saved because the Goddess was smiling down on me and I didn't rely on just one form of backing up my work.
It is highly suggested that you do not depend on a single form of back up. Life is strange. You just never know what can happen.
You may be familiar with some of the apps below. Others might be new to you. Utilize as many as you can.
Back up your work with these cloud services (in no particular order):
Dropbox (Windows, Mac)
SpiderOak (Windows, Mac)
Windows Live Mesh w/Skydrive (Windows, Mac)
iCloud [formerly iDisk/Mobile Me] (Windows, Mac)
Or with these Hardware methods:
Time Machine (Mac)
External Hard Drive
Consider printing out a hard copy of your manuscript
Any time you plan on making major edits to your work, create a copy of that file first and save it somewhere else on your computer as a backup. That way if something goes wrong with the original file you'll always have that duplicate file as a backup.
Make backing up your work a routine, and stay up to date. Don't procrastinate and put it off for another time.