Time Machine

I think Time Machine is the best backup program I have ever seen for ANY computer.  Buy a usb hard drive.  Hook it up to your Mac.  It will ask you if you want to use the hard drive for Time Machine.  Answer yes, and that’s basically it.  If you just bought a Mac, it’s the first thing you should do after you set it up.
Pros: Everything is backed up, including all your programs.  If you had to replace your Mac, you can restore with Time Machine, and your new Mac is exactly like your old Mac.  Programs, settings, data….
Cons: Your backup is right next to your Mac.  In a fire or theft, you’ve lost both of them.

Online Backup

I love Carbonite.  Takes all the “important” files on your Mac and stores them on a server.  Only costs about $50/year (cheaper if you agree to 2 or 3 years).  Information on your computer is constantly backed up.  You can choose what to backup and what not to backup.  Restoring files and folders is EASY!  There is no limit to how much you can backup.
Cons: It is not a fast backup or restore.  If you have to backup large amounts of data (10GB or more) it can take DAYS to restore)  Your information is stored on a server that you have no control over.  Is it secure?  Yes!  It’s as secure as your bank information (which is stored on a server on the Internet!)  Carbonite only keeps 3 months of backups.  And when you think security…just how secure is your current computer?