thanks for your question, Richard:
apple does make and sell a specially branded back-up device called the “Time Capsule,” but it is NOT required to backup your Mac. It’s simply another option (with some cool features) that they’ve offered the marketplace. Since you have an apple portable, it’s worth looking into. In a nut shell, it serves as a wireless base station for your home, and has a 500GB or 1TB hard drive built in. the TC is capable of backing up wirelessly as long as you are in your home’s wireless network. Granted, it’s not as fast as if you had a drive plugged directly into your Mac, but it’s great if you don’t have a typical resting station, desk, office or space for your mac. Or, if you have several Macs in your home and would like them all to back-up in one place.

…

That being said, this little brief will concentrate on external hard drives that you will physically plug into your Mac or MacBook: There are many brands of external hard drives available in retail stores and on the internet. Many have all kinds of whiz-bang features, that you won’t need; Most are very reasonably priced. Get the biggest drive you can afford, but shoot for at least 250GB or more. 500GB seems to be the standard that most people are buying these days, although a quick search on amazon shows a wonderful drive (that i’ve used) at 1TB for under $90. that is a LOT of space and NOT a lot of money.

most drives will come bundled with information and instructions (some for using with windows and/or macs). you can disregard these installation CDs and instructions. there is little likelihood that you’ll need to use them with your Mac. Installing any provided software will likely just confuse the computer and bog you down with unnecessary applications (same is true with most MP3 players, digital cameras, camcorders, etc). Skip the installer CDs.

Now, just plug the power into the wall/drive and then connect the USB or FireWire cable (depending on the drive that you purchased…) from the drive to your computer. Once connected to your MacBook, you’ll see the drive icon appear on the desktop. Chances are, an alert about “Time Machine” will pop up too. The OS assumes that a major drive like this would likely be used for backing up, and offers “one-click” setup.

Choose “Use as Backup Disk”:

the Time Machine will now start to take action. The initial set-up will take a while, depending on how many files your computer contains. this is normal, and you can continue to use your computer as it works in the background (just make sure to keep the drive  and computer powered on and connected). that’s it.

once the backup process is complete, and if/when you wish to disconnect the backup drive, highlight the drive icon (on your desktop) and drag it to the trash. the trash icon will turn into an eject symbol and will allow you to unmount the drive so that you can safely disconnect it.

now, since you have a portable, chances are good that you won’t leave the drive attached to your computer all the time (certainly not while traveling). it’s best to have the drive set-up at your desk, where it won’t be moved around much…and also close to where your MacBook would typically live (so that you can connect it easily).

your Mac is smart, so subsequent backups are much faster. leave the drive connected whenever you can (and be aware that the computer must be on and awake for the backups to happen). i only unplug my backup drive when i’m taking my MacBook somewhere other than my desk. If you don’t connect your drive after 10 days, you will get a general alert from the Mac indicating that it’s been a while since it has backed things up, and it will encourage/remind you to connect again.

obviously, keeping it connected promotes frequent back-ups and will help, more so, in that dark moment of desperation & panic.

apple has a simple little tutorial of the Time Machine here too: http://www.apple.com/findouthow/mac/#timemachinebasics

Notable Considerations:
>> if you aren’t prompted to setup your Time Machine when you connect the drive that you buy, you may have to reformat the drive (a quick, simple process) before you can utilize it. Look for this quick tutorial in the Vault soon.

>> notice the TimeMachine icon in your dock and a menubar icon (at the top right of your screen)? you don’t need both. Personally, i drag the application icon out of the dock and leave the menubar icon. the menubar icon animates when things are backing up, and it provides quick access to restoring something lost (just click on it and you’ll see your options). Plus, this helps keep a tidy dock…if you ever need the actual application back, you’ll find it in your applications folder.