Step 1: Choose a free blogging software.
Read these articles from About.com Web Logs to help you choose the best blogging software for you:
Step 2: Register for an account and create your blog
These articles from About.com Web Logs provide step-by-step instructions to help you start a blog with either of the two most popular free blogging softwares - Blogger.com and Wordpress.com.
Step 3: Select Your Domain, Theme and Other Options.
During the registration process for your new blog account, you'll need to choose a domain name and blog theme. You also might want to take a few minutes before you actually start blogging to customize some of the other preferences for your blog that your blogging software allows you to modify such as the author name, comment moderation process, and so on. However, you're not required to do any customization before you start publishing blog posts.
Step 4: Start blogging.
Once you've completed steps 1-3, you're ready to join the blogosphere and start publishing content on your blog. There are many more ways you can customize your blog with plug-ins, feeds, blogrolls, and more, but these four easy steps are all you need to follow in order to start a simple blog.