Make it open source.
I really like a blog I can copy code snippits from and then adapt for my own use. For example, I recently wrote a few blog posts on apache and PHP, and I included complete code segments so that others can make use of my experiences.
You also need to keep your audience in mind. Is your readership highly technical, requiring less basic explanation but a lot of meat and potatoes, or are they novices or beginners, requiring a lot more hand-holding? You can certainly do both on the same blog, just keep that in mind while you're writing an article.
Following from that, make sure your readers don't have (any/too many) unanswered questions at the end of your article. You want them to say "Aah! That's how it works!" instead of "I still don't get it". Again, keep your readership in mind; if you're writing an article on advanced python, beginners still won't get it, but the article's not destined for them, anyway. Tagging or categorizing articles based on skill might be a very good idea.
You might want to have a look at some of the comments in the PHP documentation: identify which comments add a lot of value and which don't.