Can HN give me some pro-tips on choosing what to write about?
In either case, one tip is to keep a wiki page available, or a notepad and a pen, and as you go throughout your day, let "stuff" that you bump into spark ideas to write about later. Write those ideas down. Maybe you see a link on HN and you have a strong reaction to it... make a note, and blog about that.
If you use Quora, go back through all your Quora answers, and take some of the more interesting ones and expand them into blog posts. If you don't have any, browse Quora and see what questions catch your interest. Blog what would have otherwise been your answer.
The Quora suggestion is great! I don't have a Quora account, but I do follow links from Google to the site every once in a while, so maybe it's time I signed up.
Don't get too hung up on being an original provider of content. Few people are. Rather, think more about presentation. Anecdotes, history, even trying to spin something into a more modern context. They all matter.
Keep writing. Keep writing often. It's the only way to get better.
I think you will be very surprised as to how much people don't know. The regurgitation of information isn't a byproduct of laziness; it's a direct result of two things.
1. People don't like to read.
2. There is far, far too much noise on the web, as it is.
It may have already been said, but I'll guarantee you that only a small minority ever read it.
You could talk about what it is that you know. What it is you hope to know. Not every developer takes the same road. If your intent is to eventually position yourself as a domain expert, the rest should write itself.
You're not going to get better if you don't get started.
You could write design descriptions of your projects. What decisions did you make, and why? What was the purpose of the project? Why did you write new code instead of using something that had already been written? Etc.