Backing up your data is essential. Hard drives fail, a virus may strike, whatever the cause may be, the effect is that all your hard work, videos and irreplaceable images are gone.
Ideally a procedure for backing up should be automatic. Automatic backup means that the backup will not be forgotten at the crucial moment before their is a failure.
The first stage to starting automatic backup is to identify exactly what data needs to be backed up. Generally this will be email, videos, images and documents. If you are on windows then you already have an option available free of charge it is windows backup. Alternatively you can decide to backup mostly online, storing images on places such as flickr and switching to an online email client e.g. gmail and backing up the rest of your data online in xdrive. This pushes off the burden of ensuring your data is safe off to the provider. Note however this may not be an option if you have a slow internet connection or too much data. Also it has been known for online services to suffer data loss so this should not be seen as the only solution but rather as part of the whole automatic backup strategy. Online services also potentially provide a security risk which is not occurring if you are under complete control of your own downloads and do it all locally.
If you not using backup software and instead doing it in a manual fashion, then consider burning your data to DVD and putting them in a safe location, in a separate location from your computer. This will mitigate the issue of a fire or theft at your primary data site from losing you all your data.
If you are not sure about what data is best to backup then it may be better to take a system image often times backup software will have this included as an option, note though that this will use up the most space as it will copy everything, on your computer.
Looking for a commercial backup software solution which covers many bases Norton has Norton 360. This provides many other areas of protection as well as software backup.