Write a Blog; Don't Code One
Once you've decided that you're going to blog, the next step is to get some infrastructure in place. When you're technical, setting up a blog presents a special challenge: you're going to be tempted to create your own blogging platform from scratch at some point during the process. Ignore that temptation or you'll wind up spending months on coding up a blog, without ever writing a single blog post. You can always write new blogging software later, but start with something already available.
WordPress (either the hosted version or the version you can use on your own server) is a good first choice. There are a huge number of sites already running on WordPress, which means there's an activity community of plugin developers and theme designers, so you don't have to reinvent any wheels when you're first starting out. But there is a variety of other systems, ranging from those that require very little work, like Tumblr, to those that require some technical expertise, like Jekyll.
You can have a new blog up and running in a matter of seconds if you use a hosted option. Setting up your own server can take more time, but is entirely optional. If you can, though, it's worth investing in your own domain name, especially if you see technical blogging as a long-term strategy to boost your profile — you need to blog consistently at one domain name so that recruiters can find you easily. Getting your own name as a dotcom is the ideal when creating a professional blog. If you have a common name, however, you might want to think about versions of your name or even a separate brand with a matching domain name available.