Play as many gigs as you can. Whether it is at a local coffee house, an open-mic night or opening a concert for another band or rapper, performing live helps you hone your craft as well as exposing your music to new crowds.
Promote your live performances with fliers. This not only helps you expose your music to as many listeners as possible, but if you can help fill up a venue, club managers will begin to take notice of your work. If you're developing a following, you'll soon start to get offers to play your own concerts and be able to book better gigs.
Maximize your presence on social media to help you interact with fans. Having well-made social media profiles give you a place to see what fans like about your music and helps publicize upcoming events. Keep supporters updated on any promotions or new music.
Give away your music. Many people are hesitant to buy music from a complete unknown. Package together your best songs and release them for free on file-sharing websites. Promote these releases through your social media accounts. Giving away music generates goodwill with your fans and they'll be more likely to see you in concert if they know some of your songs.
Interact with your fans as much as possible. Stay after concerts to sign autographs or just hang out with the people that came to see you. As you build a better relationship with your listeners, they will share your music with friends or just bring your name up in conversation. A solid foundation of fans provides the base to help get your music heard by more and more people.