The demo is done and it sounds great. But now what?
You want to sell your song, right?
First, you can't sell all your rights for cash money, that's not legal.
What you can do is to attempt to get your song signed to a deal or contract. This step is often referred to as "marketing" your song.
Your first step in marketing is to make sure everyone involved in writing your song, if there are indeed other writers, has a copy. These are the people who wrote any portion of the words or melody. The folks you'll split any royalties with.
Be sure they understand how the royalties will be split and why it would be beneficial for them to help promote the song.
Ideally each co-writer then becomes a promoter and each significantly increases your chance of success. They may take it to their contacts and attempt to interest those contacts in signing the song or recording it. As co-writer you will benefit as much as they will.
Pitching is another term used to signify you are getting your song into the hands of someone who is interested in signing songs.
It's important to target your pitches.
What genre? Sub genre? What tempo? Male singer on your demo? Female?
It does you no good not the songwriting community in general to pitch a rock power ballad to A&R seeking an uptempo country song. It will not get your song signed and may close the door to them listening to additional material from you or even to outside material, period.
Obvious places to pitch or market your work include:
Music publishers
Record companies
Artists.
Less obvious? How about independent artists and label up and comers?
"But I want a hit with a famous artist!" But often a song recorded by an independent artist is the ticket to do exactly that.
How?
That indie act can get signed to a major label deal. Or a major label artist might hear the song on the indie release and decide to record it. And sometimes indie songs can become huge hits.
Other less obvious avenues to market your song: Music libraries. Film. TV Cable and streaming have been the primary drivers in a HUGE need for music.