Step 1: Plan Ahead
Don't wait until you need to use Backup to free up disk space; the app requires that you have enough free space on your hard drive to temporarily stash the files you're backing up - filling up a 4.7GB DVD with your hobbit-porn collection, for example, requires 4.7GB of free space on your hard drive. In a pinch, you can do your backup to multiple CDs instead-that way you only need one CD's worth of disk space (typically 650MB or 700MB), which Backup will reuse for each chunk of the backup. You pay the difference in time spent swapping blank CDs - not to mention the headache of keeping track of a majorly segmented backup archive.
You'll need to unlock your Keychain - it's up to you whether to Allow Once or Always Allow.
