Someone linked to someone on my effbee feed an article from The Chronicle of Higher Education about three rules for blogging. (Easy enough for you to find, should you choose to do so.)
The writer's first rule has to do with platform. F platform. If that's what you're all hot and bothered about, really, don't even bother. There are a couple of easy platforms. Choose one and start.
What he should have started with is "branding" or "marketing," since that's what he seems to think blogging's about. If you're blogging to market yourself as an academic, you better be damned good, because I don't see it working for many people that way. (But maybe we aren't marketing ourselves properly?)
So, in contrast, here are my rules for blogging.
1. Blogging is either a private journal or about community. If it's a private journal, that's all well and good. Enjoy. But if it's about community, then make sure you join the community. Put up a blog roll and include people you read, even if you don't always agree with them. It's not that hard to do. And comment on the blogs of people you read. Encourage others, recognize their work, their good ideas, their contributions. Learn from others.
--Don't be like the occasional creative writing student I've talked to who doesn't read anyone else's work, and isn't interested in anyone else's ideas, style, work. But they think someone should read their work and laud it.
It's no accident, I think, that the blogging community that I see as most interesting is largely comprised of women, some of whom blog, some of whom comment but don't blog. (If you have an urge to say "what about the menz!?!?!" right now, you should calm down. I didn't say that no men ever were good community members.)
2. Enjoy. Life is too short to do something without a good reason; enjoyment is a good enough reason to blog. If you don't enjoy it, find something else that you do enjoy.
Thus endeth the rules of academic blogging.