When I talk about my writing, I generally start with my fiction writing, because that’s what’s turned out to be important to me.
My first paid publication, though, was in Computer Gaming World, Issue 1. (1.4MB PDF)
Before I’d been published in fiction, I’d been published in technical writings of various stripes. I had a column about computers for, and I quote my editor here, “double-digit IQ types.” (Over time, I’ve actually had three technical columns.)
I was very happy to have poetry published, as I considered it the “least like me” writing style of all. Another style I didn’t expect to be published in: creative non-fiction. I rather enjoyed it once I got the hang of it.
All of those happened before my first fiction sale (which was in 1991).