Blogs are not traditional media, and bloggers are not journalists. Unless they are. But it's not a requirement. A blog is software. It's something one puts up on the Web to capture and disseminate information, of whatever type one wishes, and thus, if anyone tells you that you're doing it wrong, that's just silly. There aren't very many wrong ways to do it (except for illegal things, like stealing from others). And yet . . .
If you're going to blog seriously, keep in mind the following:
Consider the goals and value of your posts. Are you adding to a body of work? Are you blogging to educate, to inform, to deliver some value?
Facts do matter. If you're stating opinions, stress that they're opinions. If you're claiming a fact, try to cite sources. (I tend to state mostly opinions.)
Remember that defamation is still a potentially legal issue.
You can always ask questions before you blog (a novel idea, I know).
Brevity matters. I know that I blog about this often. I see a number of posts where one has to wade through to try to decipher the salient points (often my own).
Disclosure is key. If you're doing something to make money, if you have a business relationship with an organization that you're writing about, if there's anything that might potentially change the way something is perceived were it be to be measured against what you wrote, it's better to disclose that.
Link when you're mentioning other sites or information that have links. It's good manners. It's the way the Web works. It's more resources. Linking only to yourself says something about you (and it's not flattering).
Review the body of your work every 10 posts or so. Are you improving?
Review the body of your work every 30 posts or so against the most recent. Are you repeating?
Review the body of your work against five other blogs in your space. Are you an echo?
Ask yourself why you're posting what you're posting. Pretend you're the reader. Is this worth his or her time?
What else could you be doing with your blog to add value to your core community?
There are lots of reasons to be blogging: to capture your thoughts, to share moments, to build relationships, to establish thought leadership, to sell electric toothbrushes, whatever. None of them are especially wrong. But if you're going to blog with the perspective that you are a professional, give it your best. Your audience deserves it.