It helps to have something to say (it doesn't have to be brilliant, you just have to want to say it where others can read it if they're of a mind to), and you have to want to write on a regular basis to keep your own interest up.He gives a great list of ways blogs can be used in a writing class, which you should check out. Some of them are pretty basic, but you may find a couple things you hadn't thought of before. He also says:
A blog is the place where a writer can think in public, and the act of sharing thoughts is both intimate and anonymous in this space. You never know, to start, who, if anyone, will read what you write. Yet over time, most blogs will find some audience, no matter how small. And a writer who likes the writing and posting, will grow.
I totally agree with him that writing teachers and students learning to be writing teachers should try blogging. If they don't like it, they aren't required to continue. But they may find, as I did, that the world is opened up before them. Once they start, they may not want to quit.