The following is what I do to ensure that my data is never lost on my Mac:
- I use Apple's built in Time Machine backup on a portable HD. This is automatic and there is no harm in letting it do its thing. With how incredibly cheap high capacity drives are these days there is no reason NOT to do this if you own a Mac.
- I use SuperDuper to create and maintain bootable images of my Mac. In a pinch this would be an easy way to recover data from a failure.
- I subscribe to Carbonite Online Backup which stores all of my data, encrypted, off site. This is a very important step as relying solely upon local backups still leaves you vulnerable. As of this blogpost they are still working on more solid compatibility with Mac OS X 10.6 and Windows 7, which is something to keep in mind.
Other options include burning to a series of DVD's (which can be tedious to keep track of) or synchronizing to a portable HD and moving it off site periodically.
I have heard it repeated many times that if you only have one copy of something then you do not really have it at all.
Wait, what do I do if I run Windows? All you have done is offer advice to Mac people!
There is a great tool that is free from Microsoft called SyncToy. If you have a portable HD then you can use SyncToy to keep a duplicate of your critical folders from your computer. You can download a copy of SyncToy by clicking here.