This tip will either be a waste of time or it will save you more grief than you can imagine. Backing up your important information can make the difference between taking 10 minutes to restore your data versus weeks and hundreds of dollars to get none to all of it back. I lost my data once and didn't have the money to spend restoring, so I spent over a year and a half trying out different software and techniques before I was finally able to rebuild the data I lost -- a lot of irreplacable pictures.
So now that you know you should be backing up your data, how do you do that? The first step is to identify what you want to back up. This isn't as easy as it might sound at first. Things tend to get scattered all across your hard drive, floppies, CDs, etc. The only thing worse than not backing up anything is backing up everything but a key document -- by the time you realize you've lost it, it may be be too late to recover. Once you've got it all collected, find a spot on your hard drive where you can store everything.
Now that the first step is completed, it's time to look at your backup options. Which backup method you choose is largely a matter of personal preference. The four general ways to backup data are online, nearline, offline, and offsite. There are benefits to each, as well as drawbacks. Here are some brief descriptions.
Online storage backups are not really backups, they are redundancies in the way the data is stored, meaning that a single dead hard drive does not lead to data loss. However, for the purposes of our discussion, it can be considered a method of backup. Typical online storage would be something like an internal RAID with fault tolerance, NAS/SAN, or some other method of keeping data instantly accessible and current in the event of a failure. Also, you don't have to think about performing backups, data is automatically backed up whenever you change or update it. However, in the event of a complete system failure, all information will be lost. This could be due to theft, lightning and other natural disasters, structure failure, fire, etc.
Nearline storage allows you to keep data close at hand, but not fully current or instantly accessible. This would be a true replication of data, so that it exists both on the computer and on another device. Typical nearline storage devices are USB flash drives, external hard drives, secondary internal hard drives, or any other type of storage usually connected to the computer or across a network. The backed up data is quick and easy to access in the event of a primary storage failure. This type of backup is probably most common in home environments.
Offline storage is that which is backed up, usually on removable media such as blank CDs or DVDs (optical media), floppy disks, zip disks, storage tapes, etc. These media are easily stored elsewhere, since they are typically much cheaper and more portable than the other solutions. Offline storage requires that you locate the media and put it in a reader attached to your computer. One of the biggest problems with this type of storage is that sometimes the media goes bad. This is especially true for optical media.
Offsite storage is typically an offline storage system where some or all of the media is kept in another physical location. For example, if you backup your home computer's data to DVD and store the DVD in your desk drawer at work, you have an offsite backup. This may accomplish your goals just fine, or you may want to look at a more secure solution, such as a safety deposit box or a professional service which will pick up and store your media.
Another form of offsite storage is internet-based storage. There are plenty of sites out there that will give you free storage, from free web hosts, to file sharing sites, to dedicated backup sites, to jumbo sized email hosts. Some of these are better than others for keeping backups of sensitive information. For example, the backup sites linked all claim to encrypt your data so that only you can retrieve it. In general, I don't trust proprietary encryption and I don't trust somebody else to encrypt the data for me. So you'll probably want to encrypt it before uploading (that's a topic for another day...).
While any data backup is better than none at all, I recommend keeping a few different backups using different methods. My important data resides in several locations. First, it is on my local hard drive. Once a week or so I copy this to a file server running a RAID. Every once in a while I'll copy the backup to an internet-based offline storage system. This ensures that I can survive several failures without loss of data.
Don't forget how critical your backups are! Don't store the backups where they may get stolen, lost, damaged, or otherwise be useless. Also don't forget to keep this data secured and/or encrypted. And it might be handy to test your backups regularly to make sure you can restore the information. Many businesses learn these lessons the hard way by losing their only copy of data, by having the information leak out because they treated their backups as if they were blank, or by not being able to get their data back when they really needed it. I warned you.
Businesses pracitce "Risk Management," determining an acceptable amount of risk to allow as a tradeoff for cost. But they're only protecting their money; you have to protect much more valuable property. Whether you're backing up your Great Grandmother's cookie recipé, your college thesis paper, or your pictures of your kids' first Christmas, these things are irreplacable. With the free tools outlined here, the only cost to you is your time.
The final lesson in data backup is trust. Backups are an insurance policy and the most important part of insuring against loss is trust. So don't listen to the lizard or the duck when they tell you that cheap insurance is better. The truth is that if you ever have to cash in one of these things, they'd better pay off. If you don't have 110% confidence that you can recover quickly and easily after a disaster, then it's time to start looking for somebody that you can trust to make that happen.