The easiest way to back your content up from your site is to download the XML file. You should do this anytime you have made major changes and probably once a month anyway at the least. To do so, login to your site, go to “Tools” and then to “Export.” Download the file and save it in a safe place. If you ever lose your content for any reason you can simply reverse this process and choose “import” to get all your content back.
If you want to investigate further and really delve into this check out the Word press Codex here.
If you want something more robust that’s still simple and efficient then check out Back up Buddy from iThemes here.