I have been programming for 14 years, in several languages, and I think if I am going to be serious about doing consulting work until I get my application done, then I should start a tech blog, to show what I know, basically.
But, there are many tech blogs out there, so I am not certain how to set myself apart.
I specialize in an area that is hard to describe, in that I don't adhere to any particular framework or language, but I take the visions of others, and implement them, given the constraints from whomever is paying. :)
I new love is functional programming, and I am fascinated with the fact that Java and .NET are becoming hybrid with the addition of FP languages, so I am trying to better understand how to best take advantage of this in various types of problems.
I am also exploring where DSLs can be useful for non-technical people, to help them write applications.
Just write about what interests you. If you aren't interested in the topics youa re going to get bored/tired/etc. People like to read stuff that is done with energy and passion. your blog will get old and stale if you are not interested in the topics - either you will do a crappy job or you just won't do it at all.
Write what you are passionate about. (and, second to that - Write what you know.)
I would focus on picking a fight.
http://gettingreal.37signals.com/ch02_Have_an_Enemy.php I don't have a clear path to accomplish that in a tech blog. But what about reviewing some open source projects and tearing them to shreds :) I know. It's mean. It's going to piss people off, and you are going to get some terrible comments. But if you do some good by providing something constructive during this, you'll find fans that adore you for the help.
It's maybe not the most altruistic attitude about blogging, but I think it's probably in the top 3 reasons for 37signal's success.
They tend to create these conflicts by having positions that are contrarian to what a bunch of other people feel. So it generates a huge amount of debate. Sure a bunch of people hate 'em, but then a bunch of people love 'em and carry their messages far and wide.
See this other questions: http://answers.onstartups.com/questions/2794/why-is-my-tech-blog-not-taking-off May give you some idea of the struggle ahead.
I think you are best off with general programming concepts, and you can illustrate the point of your post with your knowledge of various programming languages. If your blog is meant to promote YOU, you should aim for the widest audience possible. Think Coding Horror, but diving deeper (more code examples that illustrate YOUR expertise), and wider if possible.
James I was also not sure what kind of blog should I write and did some experiment and then settled down with Skill Guru blog This blog is mostly about programming , tutorials , tests and certifications. And as you can see I have invited others to write the articles here.
What happens with the combined efforts of users is that the blog can address to a wider audience. Else you may keep writing articles and the search engine can never find you.
We are 6 months old and have traffic of 10k users a month. This is not very good but not a bad start.
Would you be interested in joining us and writing for Skill-guru ?
If you really want to show off what you know, maybe you should consider solving problems that people might be having in a specific language. In general, do whatever you can to pass your 14 years of knowledge to the rest of us who lack in what your expertise is. If you are regularly feeding me information that I can actually use, then I am likely to return to feed on some more valuable knowledge.
Just make sure that your content is ORIGINAL. I need to stress that because if you just find interesting stuff elsewhere and rewrite it, most likely people will just read it from where you got it from.
Valueable, original & regular information = success.