CD-ROM. This is probably the least technologically savvy way to back up your information, but there is something going for it - it can be cheaper than the other methods, and it does work. DVDs are another great method of backup. They store even more data than a CD, making them idea for backing up pictures,videos, and user profile data.
External hard drive. External hard drives are quickly becoming a steady addition to the "must have" electronic list. Just like the name implies, an external hard drive is basically a second hard drive that is outside of your computer. You connect to it either by a USB cord or through Bluetooth (for the more advanced versions), and then you can load it up with files. These external hard drives hold a huge amount of data at a reasonable price. I personally use a 250gb external drive for all my files. It also provides mobile access if you carry the hard drive with you.
Remote computer backup services. These are the newest and most technologically savvy way to back up your files. Essentially, you pay a fee to a third party, and then you can remotely back up your files any time you want. Carbonite is one of the leading hard drive backup services. They offer a mobile app for your cell phone as well. If hard drive failure strikes, be sure to use one of the methods listed above. You never know when your hard drive may fail or crash.