Backing up your Mac is important. Hard drives fail, software can mess stuff up, or a rogue four-year-old can go from playing Reader Rabbit to putting desktop files in the trash and emptying it because the unnamed child liked the satisfying sound the computer made as they trashed each file.
No matter how it happens, data loss can range from being a simple annoyance to a very expensive business-altering-disaster depending upon how well your data is backed up.
And there are a lot of people that don't back up. Some are lucky and haven't had a problem...yet. But it is not a question of will you suffer a data loss at some point, it is just a question of when.
One thing that proves that point is the number of companies that exist to recover failed hard drives. Here is a Google search on "Hard Drive Recovery." The reason there are that many companies in business is because there are a lot of people who suddenly discover their data is hosed and don't have any backups so they have no choice but to shell out to try to save their data.
Most of these companies are reputable and do good work, but you can expect to pay thousands of dollars to recover your hard drive and depending upon why it failed you could get all of your data back as one giant folder with all the files contained on the drive. You then get to spend days figuring out what they are and where they go. Or you could end up with little or nothing off the bad drive like this poor guy's experience. Needless to say, it could be a really bad and expensive situation.
Now if you really like to live dangerously, you can try what this guy did and rebuild the drive hardware, but it's not something I would suggest.
So if you aren't actively backing up, the first thing that you need to figure what data should be backed up. Things that usually fall into this category should include your photos (duh), invoicing, documents, estimates, contacts, calendars, bookkeeping, software installers and serial number, music, movies, passwords, and anything else that you would be lost without. Many of these items reside in your User folder, but double check that things aren't parked in other parts of your hard drive(s) that should be backed up.
There are two types of backup you need to think about; short-term and long-term.
Your short-term backups are for day to day backup of files that you use all the time and things that are important. If they stop working or disappear, you can go back to the version from yesterday, or the days prior and get back to a working copy of the file. Programs like Backup (for 10.4 or 10.5 users) and Time Machine (for 10.5 users) are best for this type of backup.
If you are on a desktop Mac, you can designate on of your other internal drives* as a backup. I prefer using an external drive so that if that machine dies, you can unplug the external drive and plug it into another Mac, and immediately recover the data you need until your main Mac is fixed.
One thing you never want to do is use your main (boot) drive or any partitions on it for backups. If you do that and the drive fails, there go your files and your backups. The same goes for any other drive that has critical info on it. You want the backup on a separate drive from where your originals are stored.
With Apple's Backup, you have to do a little work to decide what you want backed up and how often you want it backed up, but once you've done that it pretty much will run automatically in the background at the scheduled times. I like to have Backup run early in the morning (like 2am) when I am most likely not sitting at my computer, but I also set my computer to never go to sleep. If you have your computer sleep when you aren't using it and this happens during a scheduled backup time, it will run the scheduled backup next time your Mac is awake.
When the drive is full it will stop backing up and let you know that you need to replace the drive or erase it and start over. External hard drives are inexpensive enough that I would strongly suggest buying another drive, unplug the old one, label the dates archived on it, plug in the new one and safely store the old one just in case you ever need any of the data on it.
With Time Machine, you just tell the computer which drives you want backed up and it will do hourly backups to make sure everything is where it is supposed to be. After a few days it condenses things to one backup per day, and if you go back a month or two, it condenses them weekly. The idea being that most likely if you lose something, you will know it pretty quickly and be able to recover the most recent version of the missing file(s) but if you are going back weeks, it is probably a file that is not being updated frequently anyways.
One thing that Time Machine will eventually do if you are not careful is start delete your oldest backups when the backup hard drive gets full. Before it gets full, I suggest replacing it with a new drive and store the old one after labeling it with the dates archived on it... just in case.
Another type of backup that can be a good idea is a network backup. The easiest way is through Backup and your .Mac account. Due to space and network limitations, I only back up things like invoices and other must-have files that I would be really sunk without, but if my office burned down, I would have the data available to start rebuilding things.
But please, please, please back up your Mac. Stop reading and do it now! Well, you can finish this post, first, I suppose. There is only one paragraph left.
A good external hard drive can be bought for around $100 and Backup is free if you have a .Mac account. Time Machine is free if you have 10.5 installed on your computer. There is really no good reason to not back up, but there are plenty of reasons for regret if you don't.
