Back up all your data, regularly. That is the first law for any prudent computer user. Virus attacks, hard disk crashes and simple human errors all gobble up your precious bytes in no time. And it is no different for a blogger. In a world where easy-to-use interfaces allows you to dump all your valuable posts to oblivion in a split-second, it is all the more true.
So how do you backup your blog posts? That would mainly depend on the blog you are using. I will describe a very simple method to backup your posts in one single file from Blogger, and things shouldn't be very different for others as well.
As you might know, every blog on Blogger has a unique ID. First, find out yours. Then, type in the URL : https://www.blogger.com/atom/xx, replacing xx with your ID. You might be prompted for your Blogger username and password. Enter it and you will get all your posts in that blog, in one single XML file. Save it to your harddisk or CD and you can be assured that next time you need it, you can safely find it there. Do this on a regular basis and you will never lose another post. (And yes, I did say that it was a very simple method.)
Other blogs offering RSS, XML or Atom feeds will most probably have a similar option as well. Play around with your feed to find them. Any feedback in the comments section will be greatly appreciated.