Firstly if you’re on WordPress.com, there’s nothing to do as your blog is mobile friendly by default! You can even login as admin at http://m.wordpress.com from your mobile set. This is cool!
You just have to install one the many plugins available that will turn your site into a mobile version if it detects a mobile device or browser accessing the blog.
I have tried several solutions and the one I found simplest and favoured was MobilePress. Installation is like any other plugins. After activation, you’ll need to do a simple setup such as this:
If cache plugin is used, you may need to clear the cache to be able to see the mobile version on your mobile browser.
Here’s an example of what your site might look on a normal web browser and its mobile version:
On mobile browser: