I can type faster than I can write so I start all my posts by getting comfortable on my couch and typing on my netbook. This works for me, this may not work for you.
There are several bloggers I have spoken with on technique and they are still writing outlines on paper or main thoughts in longhand and typing up the final copies for publishing.
Follow what you did naturally before you took on the blog.
I have always written directly on my keyboard and have few paper notes, so my blog is an extension of the workflow I already had established.
Do what works, just as long as you are doing something.