My first "published" item was a 500 word letter to the editor that got printed in a newspaper.

I was 20. Procedure: Write a letter with something marginally intelligible to say, post it to the editor.
I loved seeing my words in print, and I was hooked.
My first paid published item was a piece of non-fiction (actually a 36,000 word supplement for a game). I was 34, and you wouldn't believe how many words I'd written and junked in the intervening fourteen years; millions and millions.
I wrote a few query letters, got a request for a sample, sent the sample, and got a contract a couple of days later.
The editor liked it a lot, and I liked the project; I asked if there was anything else I could do to help. He asked me if I'd do a little copy-editing for him on some other submissions, which I did, and he was pleased.
I've sent him various bits and pieces more writing since, most of which earned me a little money. Once I had that reasonably personal relationship with credible editor in that field, submissions became a matter of "attach text file to email, click send, get reply a couple of days later."
Then he retired, so I started sending my work to half a dozen editors at once--a practice for which I've been widely criticised on this site!--but it worked for me.
A year or so ago, I figured out that I'd probably earned nearly half as much from my writing as I would have done from spending that amount of time flipping burgers.
I experimented with self-publishing, with modest and indifferent success.
Now I'd like to try to turn my hand to fiction, but I'm struggling to write something that I love enough, as yet.
Edited to add: I've just realised that never in my life have I sent a submission formatted in courier.

Most people advise that you do that, though.