People often come to me asking how to backup. Or worse, they come to me not having backed up their files, and want to know if I can recover their data. While I can often help people recover their lost data, it is far better to be prepared with a backup plan. It's also much less of a mess once the data is recovered. My advice: Be Prepared! Get yourself a backup drive NOW!
Remember, if you're a Mac user, you may want to re-format the drive for better performance (these drives are by default formatted for windows). You can do this with Apple's Disk Utility, in the Utilities folder - look at the "go" menu from finder.
Apple's Leopard OS comes with "Time Machine" which can help you back up your files.
I suggest programming your backup application to do a daily backup at a time when the computer is usually on. The nice thing about daily backups is that, if you miss one, it's not a big deal. Also be sure to have your software do incremental backups, so that your entire disk isn't re-copied every time.
If you're a business you may want a more comprehensive backup plan which includes a clone of your most critical data, archives of deleted and changed data, as well as swappable drives for keeping a copy of your data safe offsite in case of fire or theft. Feel free to ask me about this.
Dan The Berkeley Mac Guy - Phone: 510 355-5381 - email: firstname.lastname@example.org