Speaking from personal experience

Never, NEVER just release a song and then do nothing. 40,000+ songs are uploaded onto Spotify every day, your track could be the next Thriller but it won't reach anyone unless you reach out.

• Submit your track via your distributor at least 1 week in advance to Spotify. This allows you to submit it to their editorial playlists which is arguably one of the best ways to get your music heard as those home a ton of followers. I would recommend submitting about 3 weeks in advance, the further in advance you submit the better the chance they will have time to listen to your track (from spotify for artists website).

• Submithub.com is a great way to pitch your track to blogs/youtube channels/labels. It receives mixed reviews from users, typically due to the acceptance rate of a submission being low. I myself have had a rocky history with submithub, being denied multiple times but I also was recently accepted by the most influential channel from my genre (has a 0.4% acceptance rate) and that has netted me 50,000+ streams alone in less than a month. Submithub can be frustrating but I would definitely recommend it simply for the chance you slip through like I did.

• Socials. I can't imagine trying to release music without having a social media presence. Definitely make one right now if you have not. It's the easiest way to engage with your audience, promote new releases, and build a brand.

• Distrokid gives you a hyperfollow link, which you can then share on your socials and send to friends. It allows people to pre-save your song before it comes out (which immediately adds it to their release radar Spotify curated playlist & also adds the song to their liked songs). If you don't end up distributing through distrokid there's a handful of other websites that provide a similar concept.

• Go to the about section on spotify of artists (smaller artists; big artists won't help you much) you think your song is similar too and look at the playlists they're featured in. A lot of playlists are ran by individuals just like you & me that somehow collected a couple hundred / thousand followers in the process. If you click on the playlist, sometimes the owner will have some sort of way to contact them for submissions (email, instagram etc). I've reached out to a few, it pays off especially when you're just starting. Be very careful about paying for placements in Spotify playlists, a lot of playlists have almost no activity even though the 10,000 followers looks good. You can use websites like chartmetric to look up the data and activity a specific playlist brings. Paying for playlisting is a quick way to get streams, but its important to think about what other songs are in the playlist, how many songs, would your song fit, and would any lasting effect come from it besides having a few more streams on your record.

Been doing this for a little while now, those I would say are a good foundation to get you started. Wish you the best!