If you are wanting to be serious about a music career and not just make a quick buck, do the below:
- Make your music as easily accessible as possible.
- Upload music to iTunes/Spotify via TuneCore or similar
- Create your Spotify Artist page
- Submit songs for playlist review within Spotify Artist page
- Create a pre-save campaign using ToneDen (or similar)
In terms of promoting, the best thing you can do is creating an Artist Instagram page and twitter. Be active on twitter, find people in your local scene and follow similar bands fans - converse with them. On Instagram use the follow/unfollow targeting similar bands, try to aim small as smaller bands typically have people who are more likely to be interested in finding new upcoming artists. Don't spam message, wait a few days before unfollow and like people's photos.