How do you start blogging? Here’s some advice:
Open Word, Google Docs, Live Writer, or some tool where you can save your notes. Evernote actually works great and is cross platform.
Mark the date and start writing about something you did this week. It can be a new solution or a description of the way you've done something for years. Take 15 minutes at a time, a couple times a week. Get a page written that explains a solution or technique.
Repeat this 9 times. When you get done, you'll have some idea on how you can produce information on what you do. Schedule these out on a blog and keep going.
As you write, get feedback from your friends on the writing, the topic, the clarity and completeness of the explanation.
Start chronicling your technical work and you might be surprised who follows along.