I used to think of posts and then write them. Generally this would happen 2-3 times a week. If I had a post in my mind and I didn't have time to write it I would start a draft (often no more than a title) to come back to another time. I think in my entire blogging career I completed maybe two of those drafts. More often, I would end up deleting them after several months.
This was not a great systems because when I am thinking of blog posts I tend to think of a lot of blog posts. I flirted with writing multiple posts and then scheduling them for every other day but that didn't fulfill my blogging needs. Once I'm done writing a post I want to publish it right away. Two days later I might be in a very different mood and that post will seem old and out of sync with my present self.
In general I try to write something everyday. This something can be a blog post, part of a paper, a review, notes to myself, even an extended email. There is something critically important about forming written words on a daily basis. Unfortunately by the middle of the semester this daily practice has been known to fall apart.
So now I've been setting some time aside each night to blog. If a thought has been floating around in my mind all day than that is what comes out. If there is nothing there, I open up a blank post and see what shows up. Of course sometimes I have something rattling around so frantically that I can't wait until the evening to get it out. Either way it is becoming an important part of my day.