One of the most important things to stay on top of is a regular system backup. If you’re new to Mac usage—or just never bothered to backup before—you’ll want to get familiar with a built-in Mac program called Time Machine. Time Machine works with your Mac and an external drive to regularly save important documents, photos, and even important system files. Apart from keeping spares of every file, Time Machine also keeps a record of how your system looked on any given day, making it easy for a full system restore if something goes wrong.

Before you get started, make sure your external drive is Mac compatible. This is done by formatting it using the Mac file format. Time Machine is found on Mac OS 10.5 (Leopard) and above. When selecting the proper hard drive to use, you’ll want one with plenty of space for repeated backups.

This how-to is done using an external hard drive dedicated to Time Machine, and a Mac that has not been set up for Time Machine backups.

Step 1: Connect your external drive

First, hook your drive up to your Mac via the proper port: Thunderbolt, USB, or FireWire, depending on your drive and your machine. Your Mac should recognize the added hardware, and a pop-up window will prompt you to your next step. The window asks if you want to use the drive to back up with Time Machine; click Use as Backup Disk. A full system backup will start immediately.

Your first full system backup will take a little while (a few hours), but regular backups will only take a fraction of this time since the drive just needs to update what’s already there and save new files. If your drive stays connected to your Mac most of the time, the scheduled hourly backups take seconds.

By default, you'll see a Time Machine icon in your menu bar—it looks like a clock with an arrow running counter-clockwise. You can prevent this icon from appearing in the Time Machine system preference. (Time Machine preference are also accessible through System Preferences.)

If Time Machine doesn’t automatically launch, if you have multiple hard drive options of where to store your backups, or if you'd like to set up a wireless Time Capsule, click on the Time Machine icon in the menu bar and a pop-up menu will appear. Select Open Time Machine Preferences, then click on the Select Disk button. Find the drive that you’d like to save your backups to, highlight it, and click Use Backup Disk.

Step 2: Configure and customize your backups

If you don’t need to save everything as a backup, you can manually select items to omit from regular backups. Just click Options from the main Time Machine window, and then the + sign on the left-hand side of the popup box titled Exclude These Items from Backups. From there, pick and choose what items you’d like to leave out, then click Exclude when finished. You’ll see the folders or individual files you selected in the large exclude list. You can change your mind on these at any time by selecting the file and clicking the minus sign.

When your external drive gets full, Time Machine will automatically erase older backups to make room for new ones. The default setting is to notify you when older backups are deleted, but if you don’t need this information, you can change it. From the same Options menu, you can also lock documents after they’ve been edited.

Step 3: Remember to launch Time Machine

Regularly using Time Machine and backing up your files is the final step. If you have a desktop Mac, you can leave your external drive plugged in—Time Machine will subtly launch and perform backups hourly. You can also manually start a backup by clicking the Time Machine icon and selecting Back Up Now. If you don’t keep your backup drive connected to your Mac, remember to hook it up on a regular basis to protect your data. The Time Machine icon will display an exclamation point when its time to perform a backup. Just like your first full system backup, Time Machine will start running as soon as your drive is plugged in.

We have several tips and tricks that help you get the most out of Time Machine.

Leah Yamshon is a Macworld staff editor.