Ask HN: How do you choose your next side project?
How do you choose when you've too many ideas?
The #1 practice in management is
https://en.wikipedia.org/wiki/Kanban
which amounts to "finish what you start". You want to have more than 1 side project at a time because you can't always make progress on it, but you don't want to have 20 in progress. I usually have 3 I've committed to, 2 of them I am really making progress on, the third is aspirational -- that's fine with me.
It's more important that you make a choice than the particular choice you make or the process that you use to make a choice.
You should pick out projects that are bite sized and have controlled risk. It is good to write a kind of program you know how to write in a new programming language or write a program you don't know how to write in an old programming language. Don't do both.
For instance I started on a chess engine last month having never written one before. I coded one up in Python quickly and I'm now working on a better one in Java (I code both languages every day) which was much quicker to kick off because I had test cases and experience. If I got the Java one as good as I want I might try rewriting it in Rust because then I'd be an experienced chess programmer fighting the borrow checker for the first time as opposed to being lost.
"oh, X sounds cool, let's try that!"
Of course, I should clarify that I generally have multiple side-projects going on at any given time. If I'm not getting paid for it, I let myself do whatever I feel like doing that day ^^