Best way to promote your music if you're an indie artist guide... by me.
1. Your song needs to be your best song. Otherwise everything else is ruined.
2.You need a music video, cheap or not it doesn't matter, the important thing is that your music video needs to be shocking, like viral material.
3. Create a "Like Page" and promote your video via Facebook paying for a "Send people to your website" ad, the link of your website will be your music video on youtube. You can do the same via other social websites if you have the money, but it's not expensive if you do it right. But Facebook and Youtube advertising services are the most important thing.
4. The thumbnail image and the title of the ad for your video need to be as shocking as your video.
5. After that, tell your friends, maybe they can help you spreading the video with their contacts.
6. Good luck.
This guide will be more useful than spamming every site saying "hey listen to my music please!!" Because it doesn't matter if you're the next Eminem or Tiesto, marketing is the most important thing.