Whatever’s wrong with your computer, you’re going to feel far better about it (and probably come out the other side with far less work to reproduce) if you’ve backed up your files beforehand. Mac OS X makes this process less of a hassle by including Time Machine, so you can simply assign a backup drive (or partition) and back up as often as on the hour every hour, automatically. Here’s what you do:
1. Get your hands on a large, reliable external drive (there are some here. If your Mac has a second internal drive you can use this for backup instead – any drive other than the one you want to back up will do.)
2. Make sure it’s empty, as Time Machine will ask you to erase any files already on there before using the drive for backup.
3. Wait until dark – the first backup takes a while, especially if there’s a lot on your Mac, so it’s best done overnight.
4. Connect the drive to your Mac. If it’s the first time you’ve connected the drive to your computer, you’ll see a pop up asking you if you want Time Machine to use it as a backup drive. Click ‘Use as Backup Disk’.
5. If you’ve connected the drive before, click the Time Machine icon in your dock.
6. Set the slider in the Time Machine Window to ‘on’ and click ‘Select Backup Disk’
7. Select your drive from the drop down list and click ‘Use for Backup’.
8. The Time Machine Preferences window will open. Lion OS X users can click ‘Encrypt Backup Disk’ to encrypt the drive using FileVault2.
9. Click ‘Back up Now’.
10. Kick back and watch the progress bar. Your first backup will take a while as all the information you’re backing up has to be copied. Subsequent backups will only record changes since the previous backup, and so will be much faster. Time Machine stores hourly backups for the last day, daily backups for the last month and weekly backups for as long as it has space on your drive.