Some people that are new to blogging may have a misunderstanding when it comes to backing up their blog. They might backup their database and think they are covered. This only leaves you partially protected in case you experience a loss of data.
The database stores all your blog posts, comments, settings, etc. but it does not contain everything your blog may hold. Any images you use in your blog, all of your plugins and theme files, and any scripts or additional pages are not included in the database backup.
A complete backup of your WordPress blog will contain your database file and every other blog file on your server. If you have a copy of all these files then you will always be able to restore your blog in case a disaster strikes.
There are plugins available that make backing up your database a breeze. Wordpress Database Backup creates a quality backup of your blog database and is easy to use. In WordPress 2.7, simply navigate to Tools > Backup and download a copy of your database to your computer.
After that, you should download a copy of all the files on your blog to your computer as well. I use my favorite FTP program to connect to my server and do this. Most, if not all, of the files you want to backup can be found in your “wp-content” folder and if you are knowledgeable in what you’re doing then this may be all that needs to be saved. But for purposes of simplicity and to ensure that all necessary files are backed up you may just as well download all blog files from your server.
By making a complete backup of your blog you will never find yourself in the situation where your blog or parts of your blog are lost forever. Just always remember that your blog backups consist of more than just the words that you publish!