You, the songwriter, is the most important listener to your song. You should begin every song with the intention of writing a song that makes yourself go “Wow!”
If you are blown away by your own song, that song has a fighting chance in today’s crowded world. Tastes vary, but no one is so completely unique to an extent that no other listener will hear what you hear in your song.
But you have to be honest in your assessment, though. I myself use the first-listen of the day to gauge where my music is at. Any time you take a break from your song, the first time you listen to it after that gives you the freshest perspective. Recording it and listening to it as if you would any other artist. Does it blow you away? Does it make you go “I must own this music, and I must support the artist who made this.”
If you can get your song to that level of impactfulness, then the rest is a matter of finding those who have similar tastes. That’s the marketing/promotion aspect of the music business, and it’s very important, but you’d have a hard time spreading the word about offerings that aren’t impactful, or worth paying attention to. Generally speaking, the less impactful your offering is, the more marketing muscle/genius you have to inject into the equation, to make it work. A true brilliance, a fully realized impactfulness can incite excitement from even those who casually glance at it (though not always — some masterpieces require investment of time to begin to appreciate its value).
But it all starts with the very first listener of the song, who is the person who wrote the song. Does it honestly blow you away? If not, why not? Is the material not that strong to begin with, or does it have potential but not really coming together?
I have some ideas about how to help you with the latter. Stay tuned.