Blogging is not just about getting your message across. It's also for communication - other people can comment on what you have written, or respond to you on their own blog and link back to you. This is a public discourse. It could also be a way of starting arguments.
By now we have a nice list of staff blogs. You may not know which blog belongs to which person, but you can take a look at the blogs and see what they've written.
Go into a few other people's blogs and leave some comments. You may offer a word of encouragement, or read some people's reasons for blogging and tell them what you think of it.
Other people may comment on your blog.
Blog about your experiences contributing to discussions on other people's blogs, and how you think blogs can be useful for you or the library.
You may want to keep watching some people's blogs for new posts and adding comments where-ever you feel like encouraging, helping out with a problem or responding to what they've written. There's even ways of subscribing to their blogs, but that will be covered in steps 9 to 11 of 23 Things.